1. \Gnash\, v. t. [imp. & p. p. {Gnashed}; p. pr. & vb. n.
   {Gnashing}.] [OE. gnasten, gnaisten, cf. Icel. gnastan a
   gnashing, gn?sta to gnash, Dan. knaske, Sw. gnissla, D.
   knarsen, G. knirschen.]
   To strike together, as in anger or pain; as, to gnash the
   teeth.
   
   

2. \Gnash\, v. i.
   To grind or strike the teeth together.
   
         There they him laid, Gnashing for anguish, and despite,
         and shame.                               --Milton.
   
   

Heb. harak, meaning "to grate the teeth", (Job 16:9; Ps. 112:10; Lam. 2:16), denotes rage or sorrow. (See also Acts 7:54; Mark 9:18.)