costa n 1: a riblike part of a plant or animal (such as a middle rib of a leaf or a thickened vein of an insect wing) 2: any of the 12 pairs of curved arches of bone extending from the spine to or toward the sternum in humans (and similar bones in most vertebrates) [syn: {rib}, {costa}]
Costa \Cos"ta\ (k[o^]s"t[.a]), n. [L., rib. See {Coast}.] 1. (Anat.) A rib of an animal or a human being. [1913 Webster] 2. (Bot.) A rib or vein of a leaf, especially the midrib. [1913 Webster] 3. (Zool.) (a) The anterior rib in the wing of an insect. (b) One of the riblike longitudinal ridges on the exterior of many corals. [1913 Webster]