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

Rounding out the mechanical upgrades is a revised braking system, which should come in handy on particularly treacherous routes. —Bryan Hood, Robb Report, 5 Nov. 2025

Before all that goes down, the Grand Line season will see Luffy (Iñaki Godoy) and his Straw Hats crew enter a treacherous expanse of water on new adventures, meeting all sorts of kooky characters and creatures along the way. —Nick Romano, Entertainment Weekly, 3 Nov. 2025

But with four weeks remaining in the regular season, the path ahead is treacherous. —Jon Wilner, San Diego Union-Tribune, 2 Nov. 2025

An experienced hiker from San Diego attempting to climb the tallest peak in the contiguous United States has fallen to his death amid treacherous winter conditions, leaving his two young sons and family in shock and grief. —Amanda Lee Myers, USA Today, 31 Oct. 2025

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