\Gnaw\, v. t. [imp. & p. p. {Gnawed}; p. pr. & vb. n.
{Gnawing}.] [OE. gnawen, AS. gnagan; akin to D. knagen, OHG.
gnagan, nagan, G. nagen, Icel. & Sw. gnaga, Dan. gnave, nage.
Cf. {Nag} to tease.]
1. To bite, as something hard or tough, which is not readily
   separated or crushed; to bite off little by little, with
   effort; to wear or eat away by scraping or continuous
   biting with the teeth; to nibble at.
         His bones clean picked; his very bones they gnaw.
                                               --Dryden.
2. To bite in agony or rage.
         They gnawed their tongues for pain.   --Rev. xvi.
                                               10.
3. To corrode; to fret away; to waste.

\Gnaw\, v. i.
To use the teeth in biting; to bite with repeated effort, as
in eating or removing with the teethsomething hard, unwiedly,
or unmanageable.
      I might well, like the spaniel, gnaw upon the chain
      that ties me.                            --Sir P.
                                               Sidney.