Knife  —n. (pl. Knives) 1 metal blade for cutting or as a weapon, with usu. One long sharp edge fixed in a handle. 2 cutting-blade in a machine. 3 (as the knife) surgical operation. —v. (-fing) cut or stab with a knife.  at knife-point threatened with a knife or an ultimatum etc. Get (or have got) one's knife into treat maliciously, persecute. [old english]