Treach″er‐ous (?), a. [See Treacher.] Like a traitor; involving treachery; violating allegiance or faith pledged; traitorous to the state or sovereign; perfidious in private life; betraying a trust; faithless.
Loyal father of a treacherous son. Shak.
The treacherous smile, a mask for secret hate. Cowper.
Syn. — Faithless; perfidious; traitorous; false; insidious; plotting.
— Treach″er‐ous‐ly, adv. — Treach″er‐ous‐ness, n.