The Collaborative International Dictionary of English v.0.48:

Occlusion \Oc*clu"sion\, n. [See Occlude.]
   1. The act of occluding, or the state of being occluded.
      [1913 Webster]

            Constriction and occlusion of the orifice. --Howell.
      [1913 Webster]

   2. (Med.) The transient approximation of the edges of a
      natural opening; imperforation. --Dunglison.
      [1913 Webster]

   Occlusion of gases (Chem. & Physics), the phenomenon of
      absorbing gases, as exhibited by platinum, palladium,
      iron, or charcoal; thus, palladium absorbs, or occludes,
      nearly a thousand times its own volume of hydrogen, and in
      this case a chemical compound seems to be formed.
      [1913 Webster]

WordNet (r) 3.0 (2006):

occlusion
    n 1: closure or blockage (as of a blood vessel)
    2: (meteorology) a composite front when colder air surrounds a
       mass of warm air and forces it aloft [syn: occluded front,
       occlusion]
    3: (dentistry) the normal spatial relation of the teeth when the
       jaws are closed
    4: an obstruction in a pipe or tube; "we had to call a plumber
       to clear out the blockage in the drainpipe" [syn: blockage,
       block, closure, occlusion, stop, stoppage]
    5: the act of blocking [syn: blockage, closure, occlusion]

Moby Thesaurus II by Grady Ward, 1.0:

118 Moby Thesaurus words for "occlusion":
   Jacksonian epilepsy, Rolandic epilepsy, abdominal epilepsy, access,
   acquired epilepsy, activated epilepsy, affect epilepsy,
   akinetic epilepsy, apoplexy, arrest, arrestation, arrestment,
   attack, autonomic epilepsy, blockade, blockage, blocking,
   cardiac epilepsy, check, clogging, clonic spasm, clonus, closing,
   closing up, closure, constriction, convulsion, cortical epilepsy,
   cramp, cursive epilepsy, delay, detainment, detention,
   diurnal epilepsy, eclampsia, epilepsia, epilepsia gravior,
   epilepsia major, epilepsia minor, epilepsia mitior,
   epilepsia nutans, epilepsia tarda, epilepsy, falling sickness, fit,
   fixation, focal epilepsy, foot-dragging, frenzy, grand mal,
   hampering, haute mal, hindering, hindrance, holdback, holdup,
   hysterical epilepsy, ictus, impediment, inhibition, interference,
   interruption, larval epilepsy, laryngeal epilepsy, laryngospasm,
   latent epilepsy, let, lockjaw, matutinal epilepsy,
   menstrual epilepsy, musicogenic epilepsy, myoclonous epilepsy,
   negativism, nocturnal epilepsy, nuisance value, obstruction,
   obstructionism, opposition, paroxysm, petit mal,
   physiologic epilepsy, psychic epilepsy, psychomotor epilepsy,
   reflex epilepsy, repression, resistance, restraint, restriction,
   retardation, retardment, rotatoria, seizure, sensory epilepsy,
   serial epilepsy, setback, shutdown, shutting, shutting up, spasm,
   squeeze, stoppage, stranglehold, stricture, stroke, suppression,
   tardy epilepsy, tetanus, tetany, throes, thromboembolism,
   thrombosis, tonic epilepsy, tonic spasm, torsion spasm,
   traumatic epilepsy, trismus, ucinate epilepsy, visitation