Source : Webster's Revised Unabridged Dictionary (1913)

Spasm \Spasm\, n. [F. spasme, L. spasmus, Gr. ?, from ?, ?, to
   draw, to cause convulsion. Cf. {Span}, v. t.]
   1. (Med.) An involuntary and unnatural contraction of one or
      more muscles or muscular fibers.

   Note: Spasm are usually either clonic or tonic. In clonic
         spasm, the muscles or muscular fibers contract and
         relax alternately in very quick succession. In tonic
         spasm, the contraction is steady and uniform, and
         continues for a comparatively long time, as in tetanus.

   2. A sudden, violent, and temporary effort or emotion; as, a
      spasm of repentance.

   {Cynic spasm} (Med.) See under {Cynic}.

   {Spasm of the chest}. See {Angina pectoris}, under {Angina}.

Source : WordNet®

spasm
     n 1: a painful and involuntary muscular contraction [syn: {cramp},
           {muscle spasm}]
     2: (pathology) sudden constriction of a hollow organ (as a
        blood vessel)