martyr

noun
mar·​tyr | \ ˈmär-tər How to pronounce martyr (audio) \

Definition of martyr

 (Entry 1 of 2)

1 : a person who voluntarily suffers death as the penalty of witnessing to and refusing to renounce a religion
2 : a person who sacrifices something of great value and especially life itself for the sake of principle a martyr to the cause of freedom
3 : victim especially : a great or constant sufferer a martyr to asthma all his life — A. J. Cronin