The Collaborative International Dictionary of English v.0.48:

Embolism \Em"bo*lism\, n. [L. embolismus, from Gr. ? to throw or
   put in, insert; cf. ? intercalated: cf. F. embolisme. See
   Emblem.]
   1. Intercalation; the insertion of days, months, or years, in
      an account of time, to produce regularity; as, the
      embolism of a lunar month in the Greek year.
      [1913 Webster]

   2. Intercalated time. --Johnson.
      [1913 Webster]

   3. (Med.) The occlusion of a blood vessel by an embolus.
      Embolism in the brain often produces sudden
      unconsciousness and paralysis.
      [1913 Webster]

WordNet (r) 3.0 (2006):

embolism
    n 1: an insertion into a calendar [syn: embolism,
         intercalation]
    2: occlusion of a blood vessel by an embolus (a loose clot or
       air bubble or other particle)

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "embolism":
   bar, barrier, blank wall, blind alley, blind gut, block, blockade,
   blockage, bottleneck, cecum, choking, choking off, clog,
   congestion, constipation, costiveness, cul-de-sac, dead end,
   embolus, gorge, impasse, impediment, infarct, infarction, jam,
   obstacle, obstipation, obstruction, sealing off, stop, stoppage,
   strangulation