A small mollusc with wing-like extensions to its body which it uses for swimming.
- Orders Thecosomata (with shells) and Gymnosomata (lacking shells), class Gastropoda
More example sentences
- The opisthobranchs include the sea slugs and their relatives the sea hares, sea butterflies, canoe shells, and others.
- These all feed on pteropods, or sea butterflies, one of the species most threatened by rising acidity.
- The divers visit a small skerrig surrounded by a kelp forest with nudibranchs, comb jellyfish and sea butterflies.
Definition of sea butterfly in:
- The US English dictionary