The Collaborative International Dictionary of English v.0.48:

Epilepsy \Ep"i*lep`sy\, n. [L. epilepsia, Gr. ? a seizure, the
   "falling sickness," fr. ? to take besides, seize, attack;
   'epi` upon, besides + ? to take: cf. F. ['e]pilepsie. Cf.
   Catalepsy.] (Med.)
   The "falling sickness," so called because the patient falls
   suddenly to the ground; a disease characterized by paroxysms
   (or fits) occurring at interval and attended by sudden loss
   of consciousness, and convulsive motions of the muscles.
   --Dunglison.
   [1913 Webster]

WordNet (r) 3.0 (2006):

epilepsy
    n 1: a disorder of the central nervous system characterized by
         loss of consciousness and convulsions

Moby Thesaurus II by Grady Ward, 1.0:

109 Moby Thesaurus words for "epilepsy":
   Jacksonian epilepsy, MS, Rolandic epilepsy, abdominal epilepsy,
   access, acquired epilepsy, activated epilepsy, affect epilepsy,
   akinetic epilepsy, amyotrophic lateral sclerosis, apoplexy, arrest,
   attack, autonomic epilepsy, blockage, brain disease,
   cardiac epilepsy, cephalalgia, cerebral palsy, chorea,
   clonic spasm, clonus, convulsion, cortical epilepsy, cramp,
   cursive epilepsy, diurnal epilepsy, eclampsia, emotional disorder,
   epilepsia, epilepsia gravior, epilepsia major, epilepsia minor,
   epilepsia mitior, epilepsia nutans, epilepsia tarda, epitasis,
   falling sickness, fit, focal epilepsy, frenzy,
   glossopharyngeal neuralgia, grand mal, grip, haute mal, headache,
   herpes zoster, hysterical epilepsy, ictus, ischialgia,
   larval epilepsy, laryngeal epilepsy, laryngospasm, latent epilepsy,
   lockjaw, matutinal epilepsy, menstrual epilepsy, migraine,
   multiple sclerosis, musicogenic epilepsy, myoclonous epilepsy,
   nervous disorder, neuralgia, neuritis, neuropathy,
   nocturnal epilepsy, occlusion, organic psychosis, orgasm, palsy,
   paroxysm, petit mal, physiologic epilepsy, polyneuritis,
   pressure neuropathy, priapism, psychic epilepsy,
   psychomotor epilepsy, radiculitis, reflex epilepsy, rotatoria,
   sciatic neuritis, sciatica, seizure, sensory epilepsy,
   serial epilepsy, sexual climax, shaking palsy, shingles, spasm,
   spastic paralysis, stoppage, stroke, tardy epilepsy, tetanus,
   tetany, the jerks, throes, thromboembolism, thrombosis,
   tic douloureux, tonic epilepsy, tonic spasm, torsion spasm,
   toxic psychosis, traumatic epilepsy, trismus, ucinate epilepsy,
   visitation



Bouvier's Law Dictionary, Revised 6th Ed (1856):

EPILEPSY, med. jur. A disease of the brain, which occurs in paroxysms, with
uncertain intervals between them.
     2. These paroxysms are characterized by the loss of sensation, and
convulsive motions of the muscles. When long continued and violent, this
disease is very apt to end in dementia. (q.v.) It gradually destroys the
memory, and impairs the intellect, and is one of the causes of an unsound
mind. 8 Ves. 87. Vide Dig. 50, 16, 123; Id. 21, 1, 4, 5.