Bruxism (teeth grinding)
Clenching or grinding the teeth. It can happen during sleep or while awake.
A little more detail
Under the 2018 international consensus, sleep bruxism is rhythmic or non-rhythmic masticatory muscle activity during sleep. Awake bruxism is defined by repetitive or sustained tooth contact and by clenching or thrusting of the lower jaw. The consensus suggests that in healthy people bruxism should be seen not as a disorder but as a behaviour that can be a risk or protective factor for certain clinical outcomes. Self-report and electromyography can be used in assessment; no standard threshold is used to say it is present or absent in healthy people.
Source: Lobbezoo F, Ahlberg J, Raphael KG et al. International consensus on the assessment of bruxism: report of a work in progress. J Oral Rehabil. 2018;45(11):837-844. doi:10.1111/joor.12663