1a long-bodied chiefly marine fish with a cartilaginous skeleton, a prominent dorsal fin, and tooth-like scales. Most sharks are predatory, though the largest kinds feed on plankton, and some can grow to a large size.
Several orders (or superorders) of the subclass Elasmobranchii: many families
2a small SE Asian freshwater fish with a shark-like tail, popular in aquaria.
Two species in the family Cyprinidae: the small red-tailed black shark (Labeo bicolor), and the larger black shark (Morulius chrysophekadion)
3a light greyish-brown European moth, the male of which has pale silvery hindwings.
Genus Cucullia, family Noctuidae: several species
[no object]British informal
(typically of a man at a social gathering) be in active pursuit of a sexual partner:as soon as he arrived he was sharking among the women