Dictionary

treacherous en · ADJ

Pronunciation

• (US) audio
• /ˈtɹɛt͡ʃɹəs/
• /ˈtɹɛt͡ʃəɹəs/

Etymology

From Old French trecheros, tricheros (“deceitful”), equivalent to treacher + -ous. See treacher.

Meanings

1. Exhibiting treachery.
   • I see the wife misused by her husband, I see the treacherous seducer of young women, / I mark the ranklings of jealousy and unrequited love attempted to be hid […] 1855, Walt Whitman, Leaves of Grass:
2. Deceitful; inclined to betray.
3. Unreliable; dangerous.
   • Work on the muskeg resulted in the formation in the first instance, and later in lengths of newly-laid track disappearing without trace into the treacherous bog. 1959 March 14, “New Railways in Quebec”, in Railway Magazine, page 202:
   • a treacherous mountain trail
   • It is standard practice for search and rescue authorities to ask other vessels in the area to assist. Usually, this is done. The weather on the night of 31 December was too atrocious, and when at 11pm the Coast Guard asked the crabber Ruff & Reddy to head to the scene, its skipper refused, as a skipper has a right to do if he believes conditions to be too treacherous. 2025 October 21, Rose George, “‘I knew in my head we were dying’: the last voyage of the Scandies Rose”, in The Guardian, archived from the original on 18 Dec 2025:
   • There are many treacherous paths leading toward history’s realms of darkness, but when it comes to routes hacked out by imperialist powers in the Congo, we really do seem near darkness’s heart. 2009 March 30, Edward Rothstein, “Casting a Sliver of Light on the Heart of Darkness”, in The New York Times, archived from the original on 27 Jul 2020:
   • […] they stood in the region of perpetual snow, amidst the glittering, treacherous glaciers and crevasses, with vast slippery-pathed precipices yawning round. 2002, Charles Morris, The San Francisco Calamity:

Forms

Antonyms

loyal · fidelitous · leal · loyal · faithful · true · untreacherous · steadfast · untraitorous

Deriveds

treacherousness · treacherous turn · untreacherous · treacherously

Hypernyms

wily · deceptive · disobedient · evil

Hyponyms

two-timing · restive · insubordinate · cheating · seditious · subversive · inconstant · adulterous · rebellious · contumacious

Relateds

trickster · betray · trick · tricky · treacher · treachery · betrayal · betrayer

Synonyms

Judasly · double-crossing · traitorsome · false · fraudulent · guileful · jeopardous · double-faced · reptitious · unsteadfast · untrue · Punic · hot · traitorly · double-hearted · infidelitous · beguiling · viperish · perfidious · proditorious · swike · fallacious · hollow-hearted · unleal · guiled · deceptious · trothless · mendacious · traitorous · booky · faithless · traitorous · perilous · false-hearted · precarious · unfaithful · deceptory · nonfaithful · parlous · unsound · traitorlike · deceptive · Judaslike · illoyal · insidious · fraudful · dangerous · wicked · renegade · viperous · perilous · proditory · deceitful · hazardous · traitorish · dangersome · hazardous · reptilian · falseheart · treachersome · ratlike · Judaslike · periculous · dastardly · perfidious · recreant · forbidding · unsafe · unloyal · doublehearted · treacherous · risky · disloyal · disleal · double-dealing

Translations (77)

pdt roakboa (unreliable; dangerous) · es alevoso (exhibiting treachery) · grc δολερός (deceitful; inclined to betray) · cs zrádný (unreliable; dangerous) · fi petollinen (deceitful; inclined to betray) · fi petollinen (exhibiting treachery) · nl verraderlijk (exhibiting treachery) · bg предателски (deceitful; inclined to betray) · hu álnok (deceitful; inclined to betray) · pt traiçoeiro (deceitful; inclined to betray) · nb forrædersk (unreliable; dangerous) · sv förrädisk (exhibiting treachery) · kk залым (deceitful; inclined to betray) · de tückisch (unreliable; dangerous) · bg вероломен (exhibiting treachery) · az kəmfürsət (deceitful; inclined to betray) · es traicionero (unreliable; dangerous) · ru непро́чный (unreliable; dangerous) · grc προδοτικός (exhibiting treachery) · pl zdradziecki (exhibiting treachery) · ga braiteach (deceitful; inclined to betray) · it traditore (exhibiting treachery) · pt traiçoeiro (exhibiting treachery) · kk опасыз (deceitful; inclined to betray) · ru вероло́мный (exhibiting treachery) · el δόλιος (exhibiting treachery) · it sleale (exhibiting treachery) · de trügerisch (exhibiting treachery) · la perfidus (deceitful; inclined to betray) · ka გამცემლური (deceitful; inclined to betray) · ga cealgach (exhibiting treachery) · ru вероло́мный (deceitful; inclined to betray) · el προδοτικός (exhibiting treachery) · cs zrádný (exhibiting treachery) · ga cealgach (deceitful; inclined to betray) · hu áruló (exhibiting treachery) · cs ošidný (unreliable; dangerous) · fr traître (deceitful; inclined to betray) · fi petollinen (unreliable; dangerous) · da forræderisk (unreliable; dangerous) · ru ненадёжный (unreliable; dangerous) · pt fementido (exhibiting treachery) · el επίβουλος (deceitful; inclined to betray) · grc προδοτικός (deceitful; inclined to betray) · bg коварен (exhibiting treachery) · de doppelzüngig (deceitful; inclined to betray) · ka მოღალატური (exhibiting treachery) · sv trolös (exhibiting treachery) · fr traître (exhibiting treachery) · el ύπουλος (unreliable; dangerous) · ota صداقتسز (deceitful; inclined to betray) · sv förrädisk (unreliable; dangerous) · da forræderisk (exhibiting treachery) · izh pettelikko (deceitful; inclined to betray) · grc δολερός (exhibiting treachery) · sga braittech (exhibiting treachery) · pt traiçoeiro (unreliable; dangerous) · bg ненадежден (unreliable; dangerous) · es aleve (exhibiting treachery) · de verräterisch (exhibiting treachery) · nb forrædersk (exhibiting treachery) · fr traître (unreliable; dangerous) · ru преда́тельский (exhibiting treachery) · ga fealltach (exhibiting treachery) · ru кова́рный (deceitful; inclined to betray) · ga fabhtach (deceitful; inclined to betray) · ga fealltach (deceitful; inclined to betray) · ka მუხანათური (unreliable; dangerous) · izh salakavala (deceitful; inclined to betray) · de hinterlistig (deceitful; inclined to betray) · cs zrádný (deceitful; inclined to betray) · el δόλιος (deceitful; inclined to betray) · it infido (exhibiting treachery) · es traicionero (exhibiting treachery) · de verräterisch (deceitful; inclined to betray) · ka გამცემლური (exhibiting treachery) · ota صداقتسز (exhibiting treachery)