Treasonable

Part of speech: adjective (a.)

Pertaining to treason; consisting of treason; involving the crime of treason, or partaking of its guilt. Most men's heads had been intoxicated with imaginations of plots and treasonable practices. Clarendon.

Synonyms: Treacherous; traitorous; perfidious; insidious. -- Trea"son*a*ble*ness, n. Trea"son*a*bly, adv.