What does treacherous mean?
Treacherous means disloyal, deceitful, or untrustworthy, particularly when someone betrays a trust or acts in a misleadingly dangerous way. The word is often applied to people, such as a treacherous ally or a treacherous enemy, but it can also describe physical conditions that appear safe while concealing serious hazards, as in a treacherous road, path, or stretch of water. Its figurative and literal senses are closely related: just as a person may conceal danger or betrayal, an apparently dependable route or situation may conceal peril. Treacherous is generally more forceful and serious than simply suspicious, and it carries a strong implication of deliberate deception when used of a person. The word is useful for describing both moral untrustworthiness and the deceptive unpredictability of difficult terrain, weather, or circumstances.
adjectiveDisloyal or untrustworthy, especially in a way involving deception or betrayal. It can also describe something dangerously deceptive or unexpectedly hazardous.
- Disloyal, untrustworthy, or betraying of trust.
- Dangerously unreliable, deceptive, or hazardous.
"The guide warned us that the mountain path was treacherous after heavy rain."
"He proved treacherous after accepting the role of trusted adviser."
"The river was treacherous, with hidden currents that pulled swimmers downstream."
A road can be treacherous without anyone betraying you: treacherous also means dangerously deceptive, especially when conditions change unexpectedly.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does treacherous come from?
The word comes through Middle English from Old French traïtreux, meaning deceitful or disloyal, which was derived from traïtor, “traitor.” The ultimate source is the Latin traditor, a betrayer, related to tradere, “to deliver up” or “hand over.” Its modern spelling reflects the insertion of a consonant in the English form, while its core meaning has remained connected with betrayal and deception.
Related word forms
How treacherous is actually used
The word is strongly negative in both its personal and physical senses. It is commonly used to describe betrayal, deception, and dangerously uncertain conditions.