The Collaborative International Dictionary of English v.0.48:

Apoplexy \Ap"o*plex`y\ ([a^]p"[-o]*pl[e^]ks`[y^]), n. [OE.
   poplexye, LL. poplexia, apoplexia, fr. Gr. 'apoplhxi`a, fr.
   'apoplh`ssein to cripple by a stroke; 'apo` from + plh`ssein
   to strike: cf. F. apoplexie. See Plague.] (Med.)
   Sudden diminution or loss of consciousness, sensation, and
   voluntary motion, usually caused by pressure on the brain.
   [1913 Webster]

   Note: The term is now usually limited to cerebral apoplexy,
         or loss of consciousness due to effusion of blood or
         other lesion within the substance of the brain; but it
         is sometimes extended to denote an effusion of blood
         into the substance of any organ; as, apoplexy of the
         lung.
         [1913 Webster]

WordNet (r) 3.0 (2006):

apoplexy
    n 1: a sudden loss of consciousness resulting when the rupture
         or occlusion of a blood vessel leads to oxygen lack in the
         brain [syn: stroke, apoplexy, cerebrovascular
         accident, CVA]