Gnash \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.
[1913 Webster]