noun
Refers to someone who betrays their lord or country, often in a historical or dramatic context. Strongly negative connotation.
彼は主君に背いた逆賊として処刑された。
He was executed as a traitor who betrayed his lord.
歴史書には、その武将は逆
In history books, that warlord is recorded as a rebel.
Compound of 逆 (gyaku, 'reverse; oppose') and 賊 (zoku, 'bandit; rebel'). The exact historical derivation is uncertain, but the combination conveys the idea of a rebel who acts against legitimate authority.