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

• 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

When Hernán helps Julia and her young daughter, Maribel, navigate treacherous borderlands, their desperate journey triggers the wrath of a ruthless trafficking syndicate. —Matt Grobar, Deadline, 7 Oct. 2025

What began as a hiking trip with friends on the breathtaking slopes of on the Tibetan side of Mount Everest turned into a frightening ordeal for 30-year-old Feng Holiday, after a rare October blizzard left her and hundreds of hikers stranded in treacherous conditions. —Lex Harvey, CNN Money, 7 Oct. 2025

Equipment and supplies were transported to and from the site using 4x4 vehicles in what were treacherous driving conditions, per the UWFRA. —Escher Walcott, PEOPLE, 6 Oct. 2025

Earlier, the company stressed that the rugged Oshkosh Defense Palletized Load System (PLS) M1075A1 excels in extreme conditions, efficiently distributing supplies and equipment in treacherous environments using demountable flat rack cargo beds or ISO containers. —Prabhat Ranjan Mishra, Interesting Engineering, 5 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