n. 1 (in full high treason: see note below) violation by a subject of allegiance to the sovereign or to the State, esp. by attempting to kill or overthrow the sovereign or to overthrow the government. 2 (in full petty treason) hist. murder of one's master or husband, regarded as a form of treason. °The crime of petty treason was abolished in 1828; the term high treason, originally distinguished from petty treason, now has the same meaning as treason. treasonous adj.
[ ME f. AF treisoun etc., OF traïson, f. L traditio handing over (as TRADITION) ]