disloyal, untrustworthy, and likely to betray trust or confidence; treacherous behavior involves breaking promises, violating agreements, or engaging in acts that harm others despite having given one’s word or made a commitment.


US English

UK English

Part of Speech



faithless, disloyal, traitorous, deceitful, untrustworthy, double-crossing, backstabbing, perfidious, false, disloyal


faithful, loyal, trustworthy, honest, dependable, reliable

Word Forms

Part of Speech Words
Noun treachery, treacheries
Verb None
Adjective treacherous
Adverb treacherously

Example Sentences

  • The treacherous mountain terrain posed numerous challenges to the climbers, with its steep cliffs, unpredictable weather, and hidden crevices.

  • In the midst of the storm, the treacherous waves crashed against the ship, threatening to overturn it and sending the crew into panic.

  • The treacherous politician, known for his deceitful tactics and betrayal of allies, was feared by his colleagues and mistrusted by the public.

  • Walking on the treacherous ice, she proceeded with caution, aware of the slippery surface that could cause a dangerous fall at any moment.


The word “treacherous” originated from the Latin term “treacherus,” which means “full of deceit” or “guilty of betrayal.” It is formed from the root word “treachery,” which refers to dishonest or deceptive behavior. The suffix “-ous” is added to form an adjective, indicating the characteristic or quality of being treacherous.

The term “treacherous” is used to describe someone or something that is untrustworthy, deceitful, or likely to betray. It is often associated with actions or situations that pose a significant risk or danger due to their unpredictable or deceptive nature. This can include hazardous conditions, such as treacherous terrain, slippery surfaces, or volatile weather, which can lead to accidents or harm.

In a figurative sense, “treacherous” is commonly used to describe people who are deceptive, disloyal, or unfaithful. It refers to individuals who act with betrayal or undermine trust, often for personal gain or hidden motives. This can apply to relationships, friendships, or professional settings where trust and loyalty are essential.

The usage of “treacherous” emphasizes the potential harm or risk associated with the subject, highlighting the need for caution, awareness, and vigilance. It serves as a warning to be wary of deceptive or unreliable individuals or situations.