The Collaborative International Dictionary of English v.0.48:

Tetanus \Tet"a*nus\, n. [L., fr. Gr. ?, fr. ? stretched, ? to
   stretch.]
   1. (Med.) A painful and usually fatal disease, resulting
      generally from a wound, and having as its principal
      symptom persistent spasm of the voluntary muscles. When
      the muscles of the lower jaw are affected, it is called
      locked-jaw, or lickjaw, and it takes various names
      from the various incurvations of the body resulting from
      the spasm.
      [1913 Webster]

   2. (Physiol.) That condition of a muscle in which it is in a
      state of continued vibratory contraction, as when
      stimulated by a series of induction shocks.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tetanus
    n 1: an acute and serious infection of the central nervous
         system caused by bacterial infection of open wounds; spasms
         of the jaw and laryngeal muscles may occur during the late
         stages [syn: tetanus, lockjaw]
    2: a sustained muscular contraction resulting from a rapid
       series of nerve impulses