There are 2 main definitions of shark in English:

shark1

Syllabification: shark
Pronunciation: /SHärk
 
/

noun

1A 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.
More example sentences
  • This shark feeds primarily on bony fishes such as parrot, trigger, squirrel, surgeon, damsel and goat fishes as well as eels.
  • Great white sharks can grow as long as 5 meters and weigh 2,500 kilos.
  • The male sharks enter the cove with considerably more speed, driven by their single-minded drive to mate.
2A small Southeast Asian freshwater fish with a sharklike tail, popular in aquariums.
  • Two species in the family Cyprinidae: the small red-tailed black shark (Labeo bicolor), and the larger black shark (Morulius chrysophekadion)
3A light grayish-brown European moth, the male of which has pale silvery hind wings.
  • Genus Cucullia, family Noctuidae: several species, including C. umbratica

Origin

late Middle English: of unknown origin.

Definition of shark in:

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There are 2 main definitions of shark in English:

shark2

Syllabification: shark
Pronunciation: /SHärk
 
/

noun

informal
1A person who unscrupulously exploits or swindles others: Coleby was a shark, not the sort of man to pay more when he could pay less property sharks want to develop 200 acres around the site See also loan shark.
More example sentences
  • They are the cyber-era equivalents of highwaymen, sharks, cheesy protection racketeers.
  • It is a scentless, unappealing botanical fraud sold by sharks to suckers.
  • But while property sharks may be kicking up their heels, small-time Plateau landowners and their tenants are bearing the brunt.
2US An expert in a specified field: a pool shark
More example sentences
  • A few unsavory types hung at the far end of the long dark bar, and a couple of sharks were playing pool in the side room.
  • Karaoke in a place like this fits right in next to the dudes watching the game on the tube and the pool sharks getting busy upstairs.
  • Preston, a pool shark, once beat singer Willie Nelson for $300,000 in dominoes.

Origin

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

Definition of shark in: