Definition of teeth-gnasher in US English:

teeth-gnasher

noun

  • 1A person who or animal which engages in gnashing or grinding of the teeth; (figurative) a person who is (excessively) agitated or fretful about something; compare "gnasher".

  • 2A suspenseful or agonizing event, situation, etc.

Origin

Early 17th century; earliest use found in Edward Topsell (d. 1625), Church of England clergyman and author.