IPA: /næʃ/
KK: /næʃ/
To grind or strike the teeth together, often in anger or frustration.
He began to gnash his teeth in frustration when he heard the news.
Past: gnashed
Past Participle: gnashed
Gnash originates from Middle English 'gnashen', which is of uncertain origin but is thought to be imitative of the sound made when grinding teeth. The word describes the action of grinding or clenching the teeth together, often in anger or frustration.
Imagine the sound of teeth grinding together in frustration — that's what 'gnash' means.