To set the teeth together and open the lips, or to open the mouth and withdraw the lips from the teeth, so as to show them, as in laughter or scorn. Fools grin on fools.

To fix the teeth, as in anguish.

The act of closing the teeth and showing them, or of withdrawing the lips and showing the teeth.

A snare or trap.

To express by grinning. He grinned horribly a ghastly smile.&