trismus
noun
tris·mus ˈtriz-məs 
1
: involuntary contraction of the muscles of mastication (as in tetanus or Parkinson's disease)
2
: lockjaw
Word History
Etymology
New Latin, from Greek trismos gnashing (of teeth), from trizein to squeak, gnash; akin to Latin stridēre to creak — more at strident
First Known Use
circa 1693, in the meaning defined at sense 1
Medical Definition
trismus
noun
tris·mus ˈtriz-məs
: spasm of the muscles of mastication resulting from any of various abnormal conditions or diseases (as tetanus)