ecostate

Century Dictionary and Cyclopedia

1. In botany, not costate; without ribs.
2. In zoology: Having no costæ, in general; ribless.
3. Bearing no ribs, as a vertebra.

Wiktionary

1. adj. botany, of a leaf Having no ribs or nerves.

GNU Webster's 1913

1. adj. (Bot.) Having no ribs or nerves; -- said of a leaf.