treacherous C2 Topic:Describing People US /ˈtɹɛt͡ʃəɹəs/ See IPA manual Freq #11075 Meanings 1 adj Dangerous and unpredictable, especially because hidden hazards are hard to see. The icy roads were treacherous, and several cars slid off into ditches. 2 adj Likely to betray someone's trust; not loyal. His treacherous friend secretly told their rivals about the plan. Thesaurus Synonyms 1 adj · dangerous and... dangeroushazardousperilousunsafe 2 adj · likely to betray someone's... deceitfulperfidioustraitorous More bookydastardlydislealdisloyaldouble-crossingdouble-dealingdouble-faceddouble-hearteddoubleheartedfaithlessfalsefalse-hearted ↔ Opposites faithfulfidelitouslealloyalsteadfasttrueuntraitorousuntreacherous Word family Related forms betraybetrayalbetrayertreachertreacherytricktrickstertricky Common collocations most treacherous Adverb + adjective Etymology AI details From Old French trecheros, tricheros (“deceitful”), equivalent to treacher + -ous. See treacher. trecheros Old French View etymology graph -> Topics Describing People Word Formation & Derivatives External links Cambridge Dictionary Wiktionary Google Images # treacherous **Type:** Word **Level:** C2 **Part of speech:** adj **IPA (US):** /ˈtɹɛt͡ʃəɹəs/ **Frequency rank:** 11075 ## Meanings 1. Dangerous and unpredictable, especially because hidden hazards are hard to see. 2. Likely to betray someone's trust; not loyal. ## Examples - The icy roads were treacherous, and several cars slid off into ditches. - His treacherous friend secretly told their rivals about the plan. ## Synonyms - booky - dastardly - disleal - disloyal - double-crossing - double-dealing - double-faced - double-hearted - doublehearted - faithless - false - false-hearted ## Antonyms - faithful - fidelitous - leal - loyal - steadfast - true - untraitorous - untreacherous ## Related Forms - betray - betrayal - betrayer - treacher - treachery - trick - trickster - tricky ## Roots and Affixes - Root: trecheros ## Etymology From Old French trecheros, tricheros (“deceitful”), equivalent to treacher + -ous. See treacher. ## AI Etymology Treacherous is from Old French trecheros, tricheros (“deceitful”), equivalent to treacher + -ous. See treacher. The analysis is mainly morphological: the modern adjectival form is built from the named base and affix. Important recorded forms include trecheros (Old French). Current senses include dangerous and unpredictable, especially because hidden hazards are hard to see and likely to betray someone's trust; not loyal. The wider family includes related words such as betray, betrayal, betrayer, and treacher. ## Topics - Describing People - Word Formation & Derivatives markdown