yellow underwingEnglishOxford New American Dictionaryyellow underwing /ˈyelō ˈəndərˌwiNG, ˈjɛloʊ ˈəndərˌwɪŋ/ ▸ noun an underwing moth that has yellow hind wings with a black terminal band. Noctua and other genera, family Noctuidae: several species, including the large yellow underwing (N. pronuba), the larva of which is a destructive cutworm.