costate,a.Nat.Hist.|ˈkɒsteɪt| [ad. L. costātus ribbed, having ribs, f.costa rib: see -ate2 2.] Having a rib or ribs; ribbed: see costa1. 1819Pantologia, Costate leaf, in botany, a ribbed leaf.1881H. B. Brady in Jrnl.Microsc.Sc. Jan. 61 The body of the shell strongly costate.