/ ʃɑːk; NAmE ʃɑːrk/ noun
1.
a large sea fish with very sharp teeth and a pointed fin on its back. There are several types of shark, some of which can attack people swimming.
2.
( informal , disapproving ) a person who is dishonest in business, especially sb who gives bad advice and gets people to pay too much for sth
—see also loan shark
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WORD ORIGIN
sense 1 late Middle English : of unknown origin.
sense 2 late 16th cent.: perhaps from German Schurke worthless rogue, influenced by shark , the animal .