The Collaborative International Dictionary of English v.0.48:
Costate \Cos"tate\ (k?s"t?t), Costated \Cos"ta*ted\ (-t?-t?d), a. [L. costatus, fr. costa rib.] Having ribs, or the appearance of ribs; (Bot.) having one or more longitudinal ribs. [1913 Webster]WordNet (r) 3.0 (2006):
costate adj 1: (of the surface) having a rough, riblike texture [syn: costate, ribbed] 2: having ribs