01 a. Pertaining to treason; consisting of treason; involving the crime of treason, or partaking of its guilt.
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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.