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1690s, Modern Latin, from Greek trismos "a scream; a grinding, rasping," akin to trizein "to chirp, gnash."
trismus tris·mus (trĭz'məs)
A firm closing of the jaw due to tonic spasm of the muscles of mastication from disease of the motor branch of the trigeminal nerve. It is usually associated with general tetanus. Also called lockjaw.