2.NounAn upper jaw especially of humans and other mammals in which the bony elements are closely fused.
3.NounEither of the two bones that lie with one on each side of the upper jaw lateral to the premaxilla and that in higher vertebrates bear most of the teeth.
4.NounOne of the first or second pair of mouthparts posterior to the mandibles in many arthropods that are used for tasting and manipulating food.