Clench teeth is a popular phrase used to describe when we tightly press our upper and lower teeth together. There are various synonyms for the word clench teeth that one can use to diversify their vocabulary. Some of the synonyms of clench teeth include grit teeth, gnash teeth, tighten teeth, lock teeth, and press teeth. Each synonym provides a different degree of pressure, intensity, and duration of teeth clenching. For instance, people usually grit their teeth to express frustration or anger while gnashing teeth indicate a sense of aggression and irritation. Regardless of the synonym you choose, the phrase serves as a descriptive way to capture a particular facial expression.