OrgyiaOr*gy"i*a\, n. [NL., fr. Gr. ? the length of the outstretched arms. So named because, when at rest, it stretches forward its fore legs like arms.] (Zo["o]l.). A genus of bombycid moths whose caterpillars (esp. those of Orgyia leucostigma) are often very injurious to fruit trees and shade trees. The female is wingless. Called also vaporer moth.