—n. 1. an instrument for cutting, consisting essentially of a thin, sharp-edged, metal blade fitted with a handle.
2. a knifelike weapon; dagger or short sword.
3. any blade for cutting, as in a tool or machine.
4. under the knife, in surgery; undergoing a medical operation: The patient was under the knife for four hours.
—v.t. 1. to apply a knife to; cut, stab, etc., with a knife.
2. to attempt to defeat or undermine in a secret or underhanded way.
—v.i. to move or cleave through something with or as if with a knife: The ship knifed through the heavy seas.