incisor

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A tooth adapted for cutting or gnawing, located at the front of the mouth along the apex of the dental arch.

Century Dictionary and Cyclopedia

1. n. pl. incisors, incisores (-sorz, in-sī-sō′ rēz). In anatomy and zoology, an incisive or cutting tooth; a front tooth; any tooth of the upper jaw which is situated in the premaxillary or intermaxillary bone, or any corresponding tooth of the lower jaw. The name was originally given to those teeth which have sharp edges and a single fang, and are situated in front of the canines of either jaw. It is now technically used of teeth, whatever their character, which are situated as above described. When there are no upper incisors, the lower incisors are those situated nearest the symphysis of the lower jaw. Incisors are technically distinguished chiefly in mammals. Most mammals possess them in both jaws. The typical number is 6 above and below; but this number is frequently reduced to 4 or 2, sometimes to none, in one or both jaws. The number in either jaw is always even, and there is usually the same number in each jaw. A striking exception to this is seen in the ruminants, which usually have only lower incisors, biting against a callous pad in the upper jaw. (See cut under Ruminantia.) Among the most highly specialized incisors are those of the rodents or Glires, which are perennial, persistently growing from open pulps, with fangs rooted through much of the extent of each jaw, and with the cutting edges beveled like an adz; teeth of this character are sometimes termed gliriform. (See cut under Rodentia.) In dental formulæ an incisor tooth is designated by the letter i. An incisor of the milk-dentition, or deciduous incisor, is designated di. See cut under tooth.
2. Same as incisorial: as, an incisor tooth.
3. Of or pertaining to the incisor teeth: as, incisor nerves.

Wiktionary

1. n. One of the front teeth of mammals, between the canines.

GNU Webster's 1913

1. n. (Anat.) One of the teeth in front of the canines in either jaw; an incisive tooth. See tooth.
2. adj. Adapted for cutting; of or pertaining to the incisors; incisive.

WordNet 3.0

1. n. a tooth for cutting or gnawing; located in the front of the mouth in both jaws