60 Idioms for Untrustworthy

Idioms are fun phrases where the words together mean something totally different from what they say one by one. People use them to make talking and writing more colorful, exciting, and full of life. Today, you are going to learn a bunch of helpful idioms that all have to do with being untrustworthy, dishonest, and deceitful.

In this lesson, we’ll look at idioms for untrustworthy that mean being unfaithful, hiding the truth, and breaking promises. Let’s get started and explore some of these helpful expressions.

Idioms for Untrustworthy

1. Two-faced

Meaning: Someone who says nice things to your face but bad things behind your back.

For Example: He acted friendly to everyone, but his two-faced behavior left his classmates hurt. / You cannot trust someone who is completely two-faced.

Other Ways to Say: Deceitful / Untrustworthy

2. Snake in the grass

Meaning: A sneaky and untrustworthy person who pretends to be a friend before betraying you.

For Example: He took all her art supplies and then insulted her like a snake in the grass. / Watch out for a snake in the grass who doesn’t keep secrets safe.

Other Ways to Say: Traitor / Sneaky person

3. Wolf in sheep’s clothing

Meaning: Someone dangerous or untrustworthy who pretends to be harmless and kind.

For Example: He seemed sweet at first, but turned out to be a wolf in sheep’s clothing. / Beware of a wolf in sheep’s clothing in your club.

Other Ways to Say: Deceiver / Hidden enemy

4. Rotten apple

Meaning: A bad and untrustworthy person who ruins things for everyone else.

For Example: One rotten apple in the group can ruin trust for the entire classroom. / The teacher watched out for the rotten apple causing trouble.

Other Ways to Say: Bad influence / Troublemaker

5. Playing both sides

Meaning: Pretending to support two opposing groups to be dishonest.

For Example: He tried playing both sides during the club argument and lost everyone’s trust. / Playing both sides is a sign of an untrustworthy person.

Other Ways to Say: Being deceitful / Unreliable

6. Shady character

Meaning: A suspicious, dishonest, and untrustworthy person.

For Example: He refused to explain where he found the lost items, acting like a shady character. / Avoid talking to a shady character in the park.

Other Ways to Say: Suspicious person / Dishonest individual

7. Double crosser

Meaning: Someone who betrays your trust after promising to help you.

For Example: He promised to share the puzzle notes, but became a double crosser. / Trusting a double crosser always leads to disappointment.

Other Ways to Say: Traitor / Betrayer

8. Backstabber

Meaning: Someone who betrays you secretly when you trust them.

For Example: Telling the secret to rivals made him look like a total backstabber. / True friends never act like a backstabber.

Other Ways to Say: Traitor / Deceitful friend

9. Fair-weather friend

Meaning: Someone who is only friendly when things are easy and abandons you when problems start.

For Example: He only hung out during party days, proving to be a fair-weather friend. / When trouble started, his fair-weather friend walked away.

Other Ways to Say: Unreliable peer / Conditional friend

10. Full of hot air

Meaning: Someone who makes big promises they cannot or will not keep.

For Example: He promised to win every game, but everyone knew he was full of hot air. / Don’t believe his big claims because he is full of hot air.

Other Ways to Say: Boaster / Untrustworthy talker

11. Full of baloney

Meaning: Someone telling complete untruths and untrustworthy stories.

For Example: His story about visiting space was clearly full of baloney. / Stop telling tales that are full of baloney.

Other Ways to Say: Dishonest / Full of lies

12. Pulling the wool over your eyes

Meaning: Tricking or deceiving someone to keep them from knowing the truth.

For Example: He tried pulling the wool over your eyes about who broke the vase. / Don’t let tricksters keep pulling the wool over your eyes.

Other Ways to Say: Deceiving / Tricking

13. Selling someone down the river

Meaning: Betraying someone who trusted you for personal gain.

For Example: When his partner blamed him alone for the project delay, he felt sold down the river. / Trusting a friend who betrays you feels like being sold down the river.

Other Ways to Say: Betrayed / Let down unfairly

14. False friend

Meaning: Someone who pretends to care but is actually untrustworthy.

For Example: He acted nice to get notes, proving to be a false friend. / A false friend leaves you when challenges arrive.

Other Ways to Say: Untrustworthy peer / Deceitful buddy

15. Slippery as an eel

Meaning: Someone who is very tricky, dishonest, and hard to pin down.

For Example: Whenever you asked him about the missing crayons, he was as slippery as an eel. / You cannot get a straight answer from someone as slippery as an eel.

Other Ways to Say: Tricky / Dishonest

16. Can’t trust him as far as you can throw him

Meaning: Having absolute zero trust in someone’s honesty.

For Example: After he lied about his homework, I can’t trust him as far as you can throw him. / He makes so many false promises that you can’t trust him as far as you can throw him.

Other Ways to Say: Completely untrustworthy / Total liar

17. Fox guarding the henhouse

Meaning: Putting an untrustworthy person in charge of something they might steal or ruin.

For Example: Letting him guard the snack table was like putting a fox guarding the henhouse. / Appointing the cheat as club treasurer is like a fox guarding the henhouse.

Other Ways to Say: Bad choice / Unsafe assignment

18. Butter wouldn’t melt in his mouth

Meaning: Looking completely innocent while actually being sly and untrustworthy.

For Example: He looked so innocent when the cookie jar emptied, acting like butter wouldn’t melt in his mouth. / Don’t let his sweet smile fool you when butter wouldn’t melt in his mouth.

Other Ways to Say: Looking innocent / Sly person

19. Playing fast and loose

Meaning: Acting in a reckless, untrustworthy, and irresponsible way with rules.

For Example: He kept playing fast and loose with the science lab guidelines. / Playing fast and loose with club money gets people into trouble.

Other Ways to Say: Irresponsible / Untrustworthy behavior

20. Leading you down the garden path

Meaning: Tricking or misleading someone with false hopes or stories.

For Example: Promising extra recess just to make us clean was leading you down the garden path. / Don’t let his fake hints keep leading you down the garden path.

Other Ways to Say: Misleading / Tricking

21. Con artist

Meaning: A person who cheats or tricks others out of things through lies.

For Example: The smooth talker at the fair turned out to be a clever con artist. / Spotting a con artist requires checking facts carefully.

Other Ways to Say: Trickster / Cheat

22. Living a lie

Meaning: Maintaining a false, untrustworthy lifestyle built on deception.

For Example: Pretending he did all the project work meant he was living a lie. / Honesty is better than living a lie to impress friends.

Other Ways to Say: Deceptive life / False persona

23. Putting on an act

Meaning: Faking emotions or honesty to hide true untrustworthy motives.

For Example: He was just putting on an act to look helpful before stealing the idea. / Stop putting on an act and tell the truth.

Other Ways to Say: Faking / Pretending

24. Wearing a mask

Meaning: Hiding your true untrustworthy character behind a friendly face.

For Example: She discovered her partner was wearing a mask of friendship. / It takes time to see through someone wearing a mask.

Other Ways to Say: Hiding truth / Fake persona

25. Playing possum

Meaning: Pretending to be unaware or innocent while hiding tricks.

For Example: He acted like he was sleeping, but was playing possum during games. / Don’t let his quiet behavior fool you when he is playing possum.

Other Ways to Say: Faking ignorance / Pretending

26. Crocodile tears

Meaning: Fake sadness or crying used to deceive people.

For Example: He cried crocodile tears after getting caught breaking the toy. / Her fake apology was just full of crocodile tears.

Other Ways to Say: Fake crying / Insincere sorrow

27. Wolf in the fold

Meaning: An untrustworthy person hidden inside a safe, trusting group.

For Example: We realized there was a wolf in the fold when items went missing. / Finding the wolf in the fold protected the club.

Other Ways to Say: Hidden traitor / Secret enemy

28. Breaking trust

Meaning: Violating someone’s confidence and proving unreliable.

For Example: Telling the secret to everyone meant breaking trust with his best friend. / Breaking trust takes a long time to repair.

Other Ways to Say: Betrayal / Being untrustworthy

29. Playing games

Meaning: Tricking people with dishonest, untrustworthy tactics.

For Example: Stop playing games and tell me who took the puzzle piece. / He lost friends because he kept playing games with them.

Other Ways to Say: Being tricky / Deceiving

30. Running hot and cold

Meaning: Changing your attitude unpredictably, making you seem untrustworthy.

For Example: One day he is friendly, the next he ignores you, running hot and cold. / You never know what to expect when someone is running hot and cold.

Other Ways to Say: Unpredictable / Unreliable

31. Two-timing

Meaning: Deceiving someone by breaking loyalty or dating or partnering secretly.

For Example: He was caught two-timing his group partners by sharing notes with rivals. / Being accused of two-timing ruined his reputation.

Other Ways to Say: Betraying / Being disloyal

32. Double agent

Meaning: Someone who pretends to be on your side while secretly helping rivals.

For Example: Working with the other team in secret made him act like a double agent. / We discovered a double agent in our club.

Other Ways to Say: Secret traitor / Spy

33. Secretive

Meaning: Hiding information and actions behind suspicious silence.

For Example: His secretive behavior made everyone suspect he was being dishonest. / Being overly secretive destroys friendship trust.

Other Ways to Say: Hiding things / Suspicious

34. Underhanded

Meaning: Doing dishonest and sneaky things behind people’s backs.

For Example: Changing the sign-up list in secret was an underhanded trick. / Avoid underhanded tactics during elections.

Other Ways to Say: Sneaky / Dishonest

35. Deceitful

Meaning: Characterized by deliberate lying and untrustworthy actions.

For Example: His deceitful answers proved he could not be relied upon. / A deceitful person always gets caught eventually.

Other Ways to Say: Dishonest / Lying

36. Untrustworthy soul

Meaning: An individual who naturally breaks promises and lies.

For Example: Lending him valuables is risky because he is an untrustworthy soul. / An untrustworthy soul rarely keeps friends.

Other Ways to Say: Unreliable person / Liar

37. Broken promise maker

Meaning: Someone who constantly swears to do things and fails.

For Example: He earned a reputation as a broken promise maker in class. / Don’t be a broken promise maker when friends ask for help.

Other Ways to Say: Unreliable person / Liar

38. Fickle friend

Meaning: A person whose loyalty changes constantly, making them unreliable.

For Example: She changed her best friend every week, proving to be a fickle friend. / A fickle friend leaves you when things get hard.

Other Ways to Say: Unreliable friend / Inconstant peer

39. Shifty eyes

Meaning: Eyes that dart around nervously, often signaling a dishonest person.

For Example: His shifty eyes gave away the fact that he was hiding something. / Watch out for shifty eyes when someone denies breaking rules.

Other Ways to Say: Nervous glance / Suspicious look

40. Dodgy character

Meaning: A suspicious and questionable person who cannot be trusted.

For Example: He hung out near the lockers acting like a dodgy character. / Avoid making deals with a dodgy character.

Other Ways to Say: Suspicious person / Shady individual

41. Sketchy person

Meaning: Someone whose behavior seems weird, unsafe, and untrustworthy.

For Example: Giving your lunch money to a sketchy person is never smart. / His strange stories made him look like a sketchy person.

Other Ways to Say: Suspicious person / Shady character

42. Untruthful teller

Meaning: Someone who alters facts and spreads lies instead of truth.

For Example: He was known around school as an untruthful teller of stories. / Check the facts yourself rather than believing an untruthful teller.

Other Ways to Say: Liar / Fabricator

43. Fabricator of tales

Meaning: Someone who invents fake, untrustworthy stories.

For Example: The boy who cried wolf proved to be a major fabricator of tales. / Don’t listen to a fabricator of tales.

Other Ways to Say: Liar / Story maker

44. Master of deception

Meaning: Someone exceptionally skilled at hiding truth and tricking people.

For Example: The magician acted like a master of deception on stage. / He hid his lies well, earning the title of master of deception.

Other Ways to Say: Trickster / Great deceiver

45. Spin doctor

Meaning: Someone who twists facts to make untrustworthy actions look good.

For Example: He tried acting like a spin doctor to excuse missing his chores. / Don’t believe a spin doctor who twists the truth.

Other Ways to Say: Fact twister / Deceiver

46. False prophet

Meaning: Someone who makes big, untrustworthy claims about future success.

For Example: He claimed he could predict test answers, acting like a false prophet. / Ignore the false prophet and study your notes.

Other Ways to Say: Liar / False guide

47. Phony friend

Meaning: Someone who pretends to like you while acting untrustworthily.

For Example: She smiled to your face, revealing herself as a phony friend. / A phony friend disappears when you need support.

Other Ways to Say: Fake friend / Untrustworthy peer

48. Counterfeit character

Meaning: An artificial, fake person whose honesty is completely false.

For Example: His polite manners turned out to be a counterfeit character trait. / You can spot a counterfeit character when pressure starts.

Other Ways to Say: Fake person / Dishonest soul

49. Hollow promises

Meaning: Empty, untrustworthy vows that are never fulfilled.

For Example: His offer to clean the room turned out to be hollow promises. / Don’t rely on hollow promises from unreliable peers.

Other Ways to Say: Empty vows / Fake words

50. Empty words

Meaning: Speech lacking any honest meaning or trustworthy backing.

For Example: Apologies mean nothing when they are just empty words. / He made grand claims that amounted to empty words.

Other Ways to Say: Meaningless talk / False vows

51. Broken pledge

Meaning: An official promise that an untrustworthy person shattered.

For Example: Signing the rule sheet and breaking it later was a broken pledge. / Keeping your word prevents a broken pledge.

Other Ways to Say: Broken vow / Shattered promise

52. Pure dishonesty

Meaning: The absolute peak state of being totally untrustworthy and false.

For Example: Stealing the test answers was an act of pure dishonesty. / Building friendships requires avoiding pure dishonesty.

Other Ways to Say: Total deceit / Complete lies

53. Shifty behavior

Meaning: Actions that look sneaky, hidden, and completely untrustworthy.

For Example: His shifty behavior near the prize box made the teacher suspicious. / Watch out for shifty behavior during games.

Other Ways to Say: Sneaky actions / Suspicious conduct

54. Unreliable partner

Meaning: Someone you cannot count on to complete shared tasks.

For Example: Working with an unreliable partner made the project take twice as long. / Avoid choosing an unreliable partner for group work.

Other Ways to Say: Untrustworthy helper / Poor teammate

55. Untrustworthy nature

Meaning: An inner character trait marked by frequent lying and deceit.

For Example: His untrustworthy nature showed when he stole the crayon box. / People avoid him due to his untrustworthy nature.

Other Ways to Say: Dishonest character / Unreliable trait

56. Deceptive smile

Meaning: A friendly facial expression hiding malicious or untrustworthy motives.

For Example: He welcomed us inside with a deceptive smile before playing a trick. / Don’t trust a deceptive smile.

Other Ways to Say: Fake grin / Sly look

57. Mask of honesty

Meaning: Faking righteousness while acting totally untrustworthily.

For Example: He wore a mask of honesty while taking supplies from the desk. / Stripping away his mask of honesty revealed a cheat.

Other Ways to Say: Fake truth / Deceptive front

58. Treacherous trail

Meaning: Actions or paths filled with betrayal and untrustworthy traps.

For Example: Trusting his shady plan led us down a treacherous trail of lies. / Avoid a treacherous trail of dishonesty.

Other Ways to Say: Betrayal path / Dangerous deceit

59. Two-faced nature

Meaning: The inherent trait of being pleasant and dishonest simultaneously.

For Example: Her two-faced nature made everyone keep their distance. / Recognizing a two-faced nature saves you from betrayal.

Other Ways to Say: Deceitful trait / Two-faced character

60. Ultimate deceiver

Meaning: The absolute peak description of an untrustworthy liar.

For Example: In the mystery story, the villain turned out to be the ultimate deceiver. / He was labeled the ultimate deceiver after the truth came out.

Other Ways to Say: Master liar / Chief cheat

Exercise to Practice

1. He acted friendly to everyone, but his ________ behavior left his classmates hurt.
2. He took all her art supplies and then insulted her like a ________ in the grass.
3. He seemed sweet at first, but turned out to be a wolf in ________ clothing.
4. One rotten ________ in the group can ruin trust for the entire classroom.
5. He tried playing both ________ during the club argument and lost everyone’s trust.
6. He refused to explain where he found the lost items, acting like a ________ character.
7. He promised to share the puzzle notes, but became a double ________.
8. Telling the secret to rivals made him look like a total ________.
9. He only hung out during party days, proving to be a ________ friend.
10. He promised to win every game, but everyone knew he was full of hot ________.
11. His story about visiting space was clearly full of ________.
12. He tried pulling the ________ over your eyes about who broke the vase.
13. When his partner blamed him alone for the project delay, he felt sold down the ________.
14. He acted nice to get notes, proving to be a false ________.
15. Whenever you asked him about the missing crayons, he was as slippery as an ________.

Answer Key

1. two-faced
2. snake
3. sheep’s
4. apple
5. sides
6. shady
7. crosser
8. backstabber
9. fair-weather
10. air
11. baloney
12. wool
13. river
14. friend
15. eel

Conclusion

Learning idioms for being untrustworthy helps you understand stories, character traits, and everyday expressions of deceit much better. When you know what these colorful phrases mean, you can describe dishonest people and tricky moments in your own writing.

Try using a few of these expressions the next time you talk about honesty or spot a tricky situation. Practicing them out loud is a great way to remember them and make your communication sound awesome.