Costa

n.	1.	(Anat.) A rib of an animal or a human being.
	2.	(Bot.) A rib or vein of a leaf, especially the midrib.
	3.	(Zool.) The anterior rib in the wing of an insect.

Noun	1.	costa - 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.	costa - 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) Synonyms: rib

anatomical structure, bodily structure, body structure, complex body part, structure