[un.der.wing] n (1535) 1: one of the posterior wings of an insect
2: any of various noctuid moths (esp. genus Catocala) that have the hind wings banded with contrasting colors (as red and black)--called also underwing moth
3: the underside of a bird's wing
[2]underwing adj (1896): placed or growing underneath the wing "~ rockets"