treasonable Meaning, Definition & Usage

  1. adjective satellite having the character of, or characteristic of, a traitor
    treasonous; unfaithful; traitorous; faithless.
    • the faithless Benedict Arnold
    • a lying traitorous insurrectionist

WordNet

Trea"son*a*ble adjective
Definitions
  1. 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.
    Syn. -- Treacherous; traitorous; perfidious; insidious. --Trea"son*a*ble*ness, n. -- Trea"son*a*bly, adv.

Webster 1913