The Collaborative International Dictionary of English v.0.48:

Lockjaw \Lock"jaw`\, n. (Med.)
   A contraction of the muscles of the jaw by which its motion
   is suspended; a variety of tetanus; trismus.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lockjaw
    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]