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 competing corridors have left them confused, forcing them to navigate not only the treacherous waters – facing threats from sea mines, aerial drones, and Revolutionary Guard patrol boats – but also the complex political currents across the strait. — Eleni Giokos, CNN Money, 27 June 2026

After death, the garden becomes more treacherous. — Literary Hub, 26 June 2026

For 250 years, between 1565 and 1815, the famous galleon fleet left the port of Manila for the port of Acapulco and back, traveling for months over the treacherous ocean while carrying a lucrative flow of foods, silver, fabrics and culinary traditions. — Daniel Hernandez, Los Angeles Times, 24 June 2026

As the head of a religious island community that stresses forgiveness, Sister Brigid comes dangerously close to adopting the treacherous nun persona from the source material. — Brian Davids, HollywoodReporter, 22 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