Found 2 items, similar to treacherously.
English → English (WordNet) Definition: treacherously treacherously adv : in a disloyal and faithless manner; “he behaved treacherously”; “his wife played him false” [syn: faithlessly, traitorously, treasonably, false]
English → English (gcide) Definition: Treacherously Treacherous \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. [1913 Webster] Loyal father of a treacherous son. --Shak. [1913 Webster] The treacherous smile, a mask for secret hate. --Cowper. [1913 Webster] Syn: Faithless; perfidious; traitorous; false; insidious; plotting. [1913 Webster] -- Treach"er*ous*ly, adv. -- Treach"er*ous*ness, n. [1913 Webster]