n One who willingly accepts being put to death for adhering openly to one's religiousbeliefs; notably, saints canonized after martyrdom.
n (by extension) One who sacrifices his or her life, station, or what is of great value to him or her, for the sake of principle or to sustain a cause.
n (with a prepositional phrase of cause) One who suffers greatly and/or constantly, even involuntarily.
v (transitive) To make someone into a 'martyr' by putting him or her to death for adhering to, or acting in accordance with, some belief, especially religious; to sacrifice on account of faith or profession.