treacherously
Americanadverb
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in a way characterized by faithlessness or betrayal; traitorously.
Darius of Persia was treacherously wounded by two of his own officers.
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in a way that is deceptive, untrustworthy, or unreliable.
This peak looks treacherously easy, but it has seen a recurrence of avalanches.
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in a way or to a degree that is dangerous; hazardously.
He refused to go faster than 25 mph on the treacherously winding and narrow Wildwood Road.
Other Word Forms
Derived Forms
Etymology
Origin of treacherously
Explanation
When you act treacherously, you betray someone. If you tell everyone in school your best friend's carefully guarded secret, you've behaved treacherously. Acting treacherously hurts or deceives another person, or betrays a secret or promise. A little boy might treacherously give away his sister's hiding place during a game of hide and seek — and his sister, in turn, might treacherously announce to some older kids that he's scared of the dark. In both cases, a secret has been betrayed. Treacherously comes from the adjective treacherous, with its Old French root word, trechier, "to cheat or trick."
Vocabulary lists containing treacherously
Into the Wild
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Common Sense
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Eragon
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Other notable singers included bass-baritone Robert Frazier as the Rev. John Hale, who realizes the truth too late, and soprano Kresley Figueroa as the treacherously weak-willed Mary Warren.
From The Wall Street Journal • Mar. 23, 2026
A storm blew in, drenching the stadium and making the shot put ring treacherously slippery.
From Los Angeles Times • Aug. 4, 2024
The playing surface was treacherously slippy with snow piled up around up around the touchlines and conditions barely playable.
From BBC • Sep. 11, 2023
In a statement issued late Friday, he said he was ready to find a compromise with the Defense Ministry, but “they have treacherously cheated us.”
From Washington Times • Jun. 23, 2023
From Frodo’s mind the bright morning — treacherously bright, he thought — had not banished the fear of pursuit; and he pondered the words of Gildor.
From "The Fellowship of the Ring" by J.R.R. Tolkien
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
