sea butterfly
noun
1- a small mollusc with wing-like extensions to its body which it uses for swimming翼足软体动物。
1.1
- Orders Thecosomata (with shells) and Gymnosomata (lacking shells), class Gastropoda.被壳翼足目（有甲壳）、裸体目（无甲壳）, 腹足纲。