These words all refer to the action of working the jaws and rubbing the teeth together. Grind is the most general word in the group. It means to pulverize, to reduce to fine particles, as by crushing or friction: grinding bones helps keep a dog’s teeth clean. Grind also means to rub together with a harsh or grating sound: The noise of his teeth grinding kept his wife awake all night. To grind one’s teeth in this way as a result of rage, pain or anguish is to gnash . Gnash more than grind sounds like the action it denotes, but it is often used idiomatically rather than in a literal sense: Their eviction was marked by much weeping and wailing and gnashing of teeth. Gnash also means to bite by grinding the teeth: a hungry lion, gnashing his kill.

Chew and masticate are synonymous in designating a crushing or grinding with the teeth. The difference between the two words is that masticate , in addition to being more formal than chew , is used only in reference to food that is swallowed after the crushing or grinding action. One speaks, for example, of chewing gum but never of masticating it.

Champ and its variant chomp mean to crush and chew noisily. Like gnash , they are colourful words which summon up lifelike mental images.

• The young station hand chomped his dinner with as much gusto as he displayed when rounding up a bullock.

Champ and chomp are also used idiomatically to refer to a restless biting action, and, by figurative extension, to restlessness or impatience shown in any way: a horse champing the bit; a convalescent champing at the bit in his eagerness to return to work.