Gnash (?), v. t. [imp. & p. p. Gnashed (#); p. pr. & vb. n. Gnashing.] [OE. gnasten, gnaisten, cf. Icel. gnastan a gnashing, gnsta to gnash, Dan.knaske, Sw. gnissla, D. knarsen, G. knirschen.]
To strike together, as in anger or pain; as, to gnash the teeth.
© Webster 1913.
Gnash, v. i.
To grind or strike the teeth together.
There they him laid,
Gnashing for anguish, and despite, and shame.
Milton.
© Webster 1913.