The Collaborative International Dictionary of English v.0.48:

Martyrdom \Mar"tyr*dom\, n. [Martyr + -dom.]
   1. The condition of a martyr; the death of a martyr; the
      suffering of death on account of adherence to the
      Christian faith, or to any cause. --Bacon.
      [1913 Webster]

            I came from martyrdom unto this peace. --Longfellow.
      [1913 Webster]

   2. Affliction; torment; torture. --Chaucer.
      [1913 Webster]

WordNet (r) 3.0 (2006):

martyrdom
    n 1: death that is imposed because of the person's adherence of
         a religious faith or cause
    2: any experience that causes intense suffering [syn: calvary,
       martyrdom]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "martyrdom":
   agony, anguish, atrocious pain, bane, blood, bloodletting,
   bloodshed, braining, clawing, confinement, cruciation, crucifixion,
   dealing death, destruction, destruction of life, dismemberment,
   dispatch, estrapade, euthanasia, excruciation, execution,
   extermination, flow of blood, galleys, gore, hard labor, hell,
   hell upon earth, holocaust, horror, immolation, impalement,
   imprisonment, incarceration, jailing, keelhauling, kill, killing,
   laceration, lancination, lapidation, martyrization, mercy killing,
   nightmare, passion, penal servitude, persecution, picketing,
   poisoning, purgatory, rack, railriding, ritual killing,
   ritual murder, rock pile, sacrifice, shooting, slaughter, slaying,
   stoning, strappado, taking of life, tar-and-feathering,
   the gantlet, torment, torture