1. (n.)nail a slender, rod-shaped piece of metal, typically having a pointed tip and a flattened head, made to be hammered into wood or other material as a fastener or support.
2. nail a thin, horny plate, consisting of modified epidermis, growing on the upperside of the end of a finger or toe.
4. (verb)nail attach something somewhere by means of nails "nail the board onto the wall"
5. (verb)collar, nail, apprehend, arrest, pick up, nab, cop take into custody "the police nabbed the suspected criminals"
6. (verb)smash, nail, boom, blast hit hard "He smashed a 3-run homer"
7. (verb)nail down, nail, peg succeed in obtaining a position "He nailed down a spot at Harvard"
8. (verb)breeze through, ace, pass with flying colors, sweep through, sail through, nail succeed at easily "She sailed through her exams"; "You will pass with flying colors"; "She nailed her astrophysics course"
9. (verb)pinpoint, nail locate exactly "can you pinpoint the position of the enemy?"; "The chemists could not nail the identity of the chromosome"
4. (noun)nail the terminal horny plate on the beak of ducks, and other allied birds
5. (noun)nail a slender, pointed piece of metal, usually with a head, used for fastening pieces of wood or other material together, by being driven into or through them
6. (noun)nail to fasten with a nail or nails; to close up or secure by means of nails; as, to nailboards to the beams
7. (noun)nail to stud or boss with nails, or as with nails
8. (noun)nail to fasten, as with a nail; to bind or hold, as to a bargain or to acquiescence in an argument or assertion; hence, to catch; to trap
Sense: a piece of horn-like substance which grows over the ends of the fingers and toes to protect them I've broken my nail; toe-nails; Don't bite your finger-nails.