2. (Bot.) A rib or vein of a leaf, especially the midrib.

3. (Zo÷l.) (a) The anterior rib in the wing of an insect. (b) One of the riblike longitudinal ridges on the exterior of many corals.

Cost"age (k?st"?j; 115), n. [OF. coustage.] Expense; cost. [Obs.] Chaucer.