gnash /ˈnæʃ/verb 4noun 1forms 6phrases 2 verb4 •To grind (one's teeth) in pain or in anger. •To grind between the teeth.The dog was gnashing a carpet •(figurative) To clash together violently.There they were, boiling up in snowy spouts of spray, smiting and gnashing together like the gleaming teeth of hell. — 1886 •To run away. noun1 •A sudden snapping of the teeth. formsgnashed · gnasht · gnashing · gnashes · gnasheth · gnashest Phrases with gnash gnash one's teethTo grind or strike the teeth together in anger, signaling extreme rage, frustration, pain, or ferocity. gnash upTo gnash (something) until it is mashed up; to mash something up as if by gnashing it.