Gnash is a verb that describes the action of grinding one's teeth, often due to frustration or anger. There are several synonyms for the word gnash that can convey similar meanings, such as grind, clench, grit, bite, and chomp. Each of these words describes a forceful action that involves the clenching or grinding of teeth. Other synonyms could include gnashing, grinding, scraping, chewing, and crunching. All of these words convey a sense of frustration, anger, or annoyance that results in a physical manifestation of the emotion. The choice of synonyms for gnash can be dependent on the context in which the word is used and the intensity of the emotion being conveyed.