Definition of: nail

(nāl) noun
1. A thin horny plate on the end of a finger or toe.
2. A claw, talon, or hoof.
3. A slender piece of metal having a point and a head, and used for driving into or through wood, etc., as for fastening pieces together.
4. A measure of length, 21/4 inches.
5. A callosity on the inner side of a horse's leg.
—on the nail Colloq.
1. Right away; immediately.
2. At the exact spot or moment.
3. Of immediate interest or importance; under discussion.
—v.t.
1. To fasten or fix in place with a nail or nails.
2. To close up or shut in by means of nails.
3. To secure by decisive or prompt action: to nail a contract.
4. To fix firmly or immovably: Terror nailed him to the spot.
5. To succeed in hitting or striking.
6. Colloq. To catch or seize; intercept.
7. Colloq. To detect and expose, as a lie or liar. [OE nœgel]
HUMAN FINGERNAIL
Longitudinal section
a. Nail.
b. Matrix.
c. Nailfold.
d. Epidermis.
e. Phalanx.