maxilla

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Anatomy Either of a pair of bones of the human skull fusing in the midline and forming the upper jaw.
2. n. A homologous bone of the skull in other vertebrates.
3. n. Either of two laterally moving appendages situated behind the mandibles in insects and most other arthropods.

Century Dictionary and Cyclopedia

1. n. In anatomy and zoology: A jaw or jaw-bone; a maxillary bone; especially, a bone of the upper jaw, as distinguished from the mandible. When the term is applied to both jaw-bones, they are distinguished as maxilla superior and maxilla inferior, the supramaxillary and inframaxillary bones.
2. n. Specifically, the supramaxillary bone proper, as distinguished from the premaxillary or intermaxillary, which is often fused therewith in the higher vertebrates.
3. n. In entomology, as in insects and arachnidans, one of the second pair of gnathites; either one, right and left, of the second or lower pair of horizontal jaws, next behind or below the mandibles. In the maxillæ, thus forming the under jaw of insects, may be distinguished several parts, as the basal joint or cardo, the footstalk or stipes, the palp-bearer or palpiger, and the blade or lacinia. See cuts under Hymenoptera, Insecta, and Brenthus.
4. n. In Crustacea, the right or left one of either of the two pairs of gnathites which come next after the mandibles, between these and the maxillipeds. The maxillæ of a crustacean thus correspond to those of an insect, but there is an additional pair of them.

Wiktionary

1. n. Either of the two bones that together form the upper jaw.
2. n. Arachnid mouthpart

GNU Webster's 1913

1. n. Now commonly used in this restricted sense., Now commonly used in this restricted sense. The bone of either the upper or the under jaw.
2. n. Now commonly used in this restricted sense. The bone, or principal bone, of the upper jaw, the bone of the lower jaw being the mandible.
3. n. (Zoöl.) One of the lower or outer jaws of arthropods.

WordNet 3.0

1. n. the jaw in vertebrates that is fused to the cranium