treacherous

adjective

treach·​er·​ous ˈtre-chə-rəs 

ˈtrech-rəs

1

a

: likely to betray trust : unreliable

a treacherous memory

b

: providing insecure footing or support

treacherous quicksand

c

: marked by hidden dangers, hazards, or perils

2

: characterized by or manifesting treachery : perfidious

treacherously adverb

treacherousness noun

Synonyms of treacherous

• traitorous
• unreliable
• false

Choose the Right Synonym for treacherous

faithless, false, disloyal, traitorous, treacherous, perfidious mean untrue to what should command one's fidelity or allegiance.

faithless applies to any failure to keep a promise or pledge or any breach of allegiance or loyalty.

faithless allies

false stresses the fact of failing to be true in any manner ranging from fickleness to cold treachery.

betrayed by false friends

disloyal implies a lack of complete faithfulness to a friend, cause, leader, or country.

disloyal to their country

traitorous implies either actual treason or a serious betrayal of trust.

traitorous acts punishable by death

treacherous implies readiness to betray trust or confidence.

a treacherous adviser

perfidious adds to faithless the implication of an incapacity for fidelity or reliability.

a perfidious double-crosser

Examples of treacherous in a Sentence

a treacherous act of betrayal

They were not prepared to hike over such treacherous terrain.

The snow made their hike all the more treacherous.

Discussions about money can lead couples into treacherous territory.

Recent Examples on the Web

The terrain can be treacherous, but the guide offered patience and grace for our entire group, slowing down without comment when someone was straggling and prioritizing water breaks. —Condé Nast, Condé Nast Traveler, 17 June 2026

Shinnecock’s fairways create optical illusions off the tee, the bunkering is treacherous and the greens are, in some places, designed to repel the ball from the putting surfaces. —Gabby Herzig, New York Times, 16 June 2026

Last week, after surviving nine treacherous months as Cracker Barrel's leader, Masino was able to share great news with investors –– customers are returning for their favorite foods, pancake deals and the comfort of Uncle Herschel leaning on a barrel. —Joe Kinsey Outkick, FOXNews.com, 15 June 2026

This treacherous gang has phenomenally rubbed out many signatures of independence in a very short time. —Voice Of The People, New York Daily News, 14 June 2026

Word History

First Known Use

14th century, in the meaning defined at sense 2

Rhymes for treacherous

• lecherous

Kids Definition

treacherous

adjective

treach·​er·​ous ˈtrech-(ə-)rəs 

1

a

: guilty of treachery

b

: likely to betray : unreliable

a treacherous memory

2

: giving a false appearance of safety or solidity

a treacherous stretch of bog

treacherously adverb