One who willingly accepts being put to death for adhering openly to one's religious beliefs; notably, saints canonized after martyrdom.

(by extension) One who sacrifices their life, station, or something of great personal value, for the sake of principle or to sustain a cause.

(with a prepositional phrase of cause) One who suffers greatly and/or constantly, even involuntarily.

(transitive) To make someone into a martyr by putting them to death for adhering to, or acting in accordance with, some belief, especially religious; to sacrifice on account of faith or profession.

(transitive) To persecute.

(transitive) To torment; to torture.