a horny sheath protecting the upper end of each finger and toe of humans and most other primates. a structure (such as a claw) that terminates a digit and corresponds to a nail. a slender usually pointed and headed fastener designed to be pounded in. to fasten with or as if with a nail. to fix in steady attention. CATCH, TRAP. to expose usually so as to discredit. to arrest or punish for an offense. to hit or strike in a forceful manner: WHACK sense 1a. to put out (a runner) in baseball. to perform or complete perfectly or impressively. to gain or win decisively —often used with down. to settle, establish, or represent clearly and unmistakably —often used with down. to copulate with.