Merriam-Webster Collegiate Dictionary - nail

 I. noun  Etymology: Middle English, from Old English n?gl; akin to Old High German nagal ~, finger~, Latin unguis finger~, toe~, claw, Greek onyx  Date: before 12th century  1.  a. a horny sheath protecting the upper end of each finger and toe of humans and most other primates  b. a structure (as a claw) that terminates a digit and corresponds to a ~  2. a slender usually pointed and headed fastener designed to be pounded in  II. transitive verb  Date: before 12th century  1. to fasten with or as if with a ~  2. to fix in steady attention ~ed his eye on the crack  3.  a. catch, trap  b. to expose usually so as to discredit ~ed the impostor  c. to arrest or punish for an offense  4.  a. strike, hit  b. to put out (a runner) in baseball  5. to perform or complete perfectly or impressively ~ed a jump shot  6. to gain or win decisively — often used with down ~ down their consent  7. to settle, establish, or represent clearly and unmistakably — often used with down have ~ed down the artist's technique  8. usually vulgar to copulate with  • ~er noun