To gnash means to rub or grind your teeth together, especially in rage or pain. It can also refer to biting with grinding teeth. Gnashing is often associated with anger, frustration, or ferocity. The term is derived from Middle English variation on gnasten, which means "grind the teeth together," from Old Norse gnasta, which means "gnash the teeth". Examples of gnashing can be found in literature, such as fairy tales where terrible ogres gnash their teeth, or in the Bible where people gnash their teeth in anger or disappointment.