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

Members of the search-and-rescue team who helped save the friends say the area is extremely treacherous and potentially dangerous even in daylight and perfect conditions. — Charlie De Mar, CBS News, 18 Aug. 2026

The journey by sea was treacherous, and the men who knew about the Koh-i-Noor feared the curse of the stone had turned its wrath on them. — Hadley Hall Meares, Vanity Fair, 17 Aug. 2026

In the trailer, viewers are introduced to the latest batch of potentially treacherous players, all of whom board a train to Scotland to try for a prize fund worth up to $250,000. — Brenton Blanchet, PEOPLE, 17 Aug. 2026

The problem is that this summer is only a preview of the treacherous weather that lies ahead. — Eric Klinenberg, New Yorker, 17 Aug. 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