shark /ʃɑːk $ ʃɑːrk/ BrE AmE noun [countable]
[ Sense 1: Date: 1400-1500 ; Origin: Origin unknown. ]
[ Sense 2: Date: 1500-1600 ; Origin: Probably from German schurke 'bad man' ; influenced by ⇨ ↑ shark (1) ]
1 . a large sea fish with several rows of very sharp teeth that is considered to be dangerous to humans:
Sharks were circling around our boat.
shark-infested waters (=waters where there are a lot of sharks)
2 . informal someone who cheats other people out of money
pool/card shark (=someone who uses their skill at ↑ pool or cards to cheat other players out of money)
⇨ ↑ loan shark