The Collaborative International Dictionary of English v.0.48:

Paroxysm \Par"ox*ysm\, n. [F. paroxysme, Gr. ?, fr. ? to
   sharpen, irritate; para` beside, beyond + ? to sharpen, from
   ? sharp.]
   1. (Med.) The fit, attack, or exacerbation, of a disease that
      occurs at intervals, or has decided remissions or
      intermissions. --Arbuthnot.
      [1913 Webster]

   2. Any sudden and violent emotion; spasmodic passion or
      action; a convulsion; a fit.
      [1913 Webster]

            The returning paroxysms of diffidence and despair.
                                                  --South.
      [1913 Webster]

WordNet (r) 3.0 (2006):

paroxysm
    n 1: a sudden uncontrollable attack; "a paroxysm of giggling";
         "a fit of coughing"; "convulsions of laughter" [syn:
         paroxysm, fit, convulsion]

Moby Thesaurus II by Grady Ward, 1.0:

154 Moby Thesaurus words for "paroxysm":
   Jacksonian epilepsy, Rolandic epilepsy, abdominal epilepsy, access,
   acquired epilepsy, activated epilepsy, acute pain, affect epilepsy,
   akinetic epilepsy, amok, apoplexy, arrest, attack,
   autonomic epilepsy, bite, blaze, blockage, boring pain, breakup,
   burst, cardiac epilepsy, cat fit, cataclysm, charley horse, climax,
   clonic spasm, clonus, conniption, conniption fit, convulsion,
   cortical epilepsy, cramp, cramps, crick, cursive epilepsy, cyclone,
   darting pain, diastrophism, disaster, diurnal epilepsy, duck fit,
   eclampsia, epilepsia, epilepsia gravior, epilepsia major,
   epilepsia minor, epilepsia mitior, epilepsia nutans,
   epilepsia tarda, epilepsy, epitasis, eruption, explosion,
   falling sickness, fever, fit, fit of anger, fit of temper,
   flare-up, focal epilepsy, frenzy, fulgurant pain, furor, fury,
   gale, girdle pain, gnawing, grand mal, grip, griping, gust,
   haute mal, hitch, hurricane, hysterical epilepsy, ictus, irruption,
   jumping pain, kink, lancinating pain, larval epilepsy,
   laryngeal epilepsy, laryngospasm, latent epilepsy, lockjaw,
   matutinal epilepsy, menstrual epilepsy, murderous insanity,
   musicogenic epilepsy, myoclonous epilepsy, nip, nocturnal epilepsy,
   occlusion, orgasm, outbreak, outburst, overthrow, pang, petit mal,
   physiologic epilepsy, pinch, prick, psychic epilepsy,
   psychokinesia, psychomotor epilepsy, quake, rage, reflex epilepsy,
   rotatoria, seizure, sensory epilepsy, serial epilepsy,
   sexual climax, sharp pain, shoot, shooting, shooting pain, spasm,
   spell, stab, stabbing pain, stitch, stoppage, storm, stroke,
   tantrum, tardy epilepsy, temblor, temper tantrum, tempest, tetanus,
   tetany, thrill, throe, throes, thromboembolism, thrombosis,
   tidal wave, tonic epilepsy, tonic spasm, tormen, tornado,
   torsion spasm, traumatic epilepsy, trismus, tsunami, tweak, twinge,
   twitch, ucinate epilepsy, upheaval, visitation, whirlwind,
   wrench