The Collaborative International Dictionary of English v.0.48:

Ictus \Ic"tus\, n. [L., fr. icere, ictum, to strike.]
   1. (Pros.) The stress of voice laid upon accented syllable of
      a word. Cf. Arsis.
      [1913 Webster]

   2. (Med.) A stroke or blow, as in a sunstroke, the sting of
      an insect, pulsation of an artery, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ictus
    n 1: a sudden occurrence (or recurrence) of a disease; "he
         suffered an epileptic seizure" [syn: seizure, ictus,
         raptus]

Moby Thesaurus II by Grady Ward, 1.0:

175 Moby Thesaurus words for "ictus":
   Alexandrine, Jacksonian epilepsy, Rolandic epilepsy,
   abdominal epilepsy, accent, accentuation, access,
   acquired epilepsy, activated epilepsy, affect epilepsy,
   akinetic epilepsy, amphibrach, amphimacer, anacrusis, anapest,
   antispast, apoplexy, arrest, arsis, attack, autonomic epilepsy,
   bacchius, beat, blockage, cadence, caesura, cardiac epilepsy,
   catalexis, chloriamb, chloriambus, clonic spasm, clonus, colon,
   convulsion, cortical epilepsy, counterpoint, cramp, cretic,
   cursive epilepsy, dactyl, dactylic hexameter, diaeresis, dimeter,
   dipody, diurnal epilepsy, dochmiac, eclampsia, elegiac,
   elegiac couplet, elegiac pentameter, emphasis, epilepsia,
   epilepsia gravior, epilepsia major, epilepsia minor,
   epilepsia mitior, epilepsia nutans, epilepsia tarda, epilepsy,
   epitasis, epitrite, falling sickness, feminine caesura, fit,
   focal epilepsy, foot, frenzy, grammatical accent, grand mal, grip,
   haute mal, heptameter, heptapody, heroic couplet, hexameter,
   hexapody, hysterical epilepsy, iamb, iambic, iambic pentameter,
   intonation, intonation pattern, ionic, jingle, larval epilepsy,
   laryngeal epilepsy, laryngospasm, latent epilepsy, level of stress,
   lilt, lockjaw, masculine caesura, matutinal epilepsy, measure,
   menstrual epilepsy, meter, metrical accent, metrical foot,
   metrical group, metrical unit, metrics, metron, molossus, mora,
   movement, musicogenic epilepsy, myoclonous epilepsy,
   nocturnal epilepsy, numbers, occlusion, orgasm, paeon, paroxysm,
   pentameter, pentapody, period, petit mal, physiologic epilepsy,
   pitch accent, primary stress, proceleusmatic, prosodics, prosody,
   psychic epilepsy, psychomotor epilepsy, pyrrhic, quantity,
   reflex epilepsy, rhetorical accent, rhythm, rhythmic pattern,
   rhythmical accent, rhythmical stress, rotatoria, secondary stress,
   seizure, sensory epilepsy, serial epilepsy, sexual climax, spasm,
   spondee, sprung rhythm, stoppage, stress, stress accent,
   stress arsis, stress pattern, stroke, swing, syzygy,
   tardy epilepsy, tertiary stress, tetanus, tetany, tetrameter,
   tetrapody, tetraseme, thesis, throes, thromboembolism, thrombosis,
   tone accent, tonic epilepsy, tonic spasm, torsion spasm,
   traumatic epilepsy, tribrach, trimeter, tripody, triseme, trismus,
   trochee, ucinate epilepsy, visitation, weak stress