(1):

(n.) One who, by his death, bears witness to the truth of the gospel; one who is put to death for his religion; as, Stephen was the first Christian martyr.

(2):

(v. t.) To persecute; to torment; to torture.

(3):

(n.) Hence, one who sacrifices his life, his station, or what is of great value to him, for the sake of principle, or to sustain a cause.

(4):

(v. t.) To put to death for adhering to some belief, esp. Christianity; to sacrifice on account of faith or profession.