Bruxism refers to teeth grinding during sleep. Bruxism is due to clenching of the teeth other than in chewing and is associated with forceful lateral or protrusive jaw movements.

This results in grinding or rubbing the teeth together. It usually occurs during sleep and sometimes done to such an excess that it damages the occlusal surfaces of the teeth, particularly the molar teeth, and may contribute to the temporomandibular joint (TMJ) syndrome. The word "bruxism" comes from the Greek "brychein" meaning "to grind or gnash the opposing rows of upper and lower molar teeth."