shark

1. a long-bodied chiefly marine fish with a cartilaginous skeleton, a prominent dorsal fin, and toothlike scales. Most sharks are predatory, although the largest kinds feed on plankton, and some can grow to a large size.
2. a small SE Asian freshwater fish with a tail resembling that of a shark, popular in aquaria.
3. a light greyish-brown European moth, the male of which has pale silvery hindwings.

1. (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

late Middle English: of unknown origin.

1. a person who unscrupulously exploits or swindles others.

   property sharks want to develop 200 acres around the site

2. an expert in a specified field.

   a pool shark

late 16th century: perhaps from German Schurke ‘worthless rogue’, influenced by shark¹.