/kos"teuh, kaw"steuh/ , n. , pl. costae /kos"tee, kaw"stee/ .
1. a rib or riblike part.
2. the midrib of a leaf in mosses.
3. a ridge.
4. Entomol.
a. Also called costal vein . a vein, usually marginal, in the anterior portion of the wing of certain insects.
b. Also called costal margin . the anterior edge or border of the wing of certain insects.
[ 1865-70; ]