noun

• (ichthyology, countable) Any predatory fish of the superorder Selachimorpha, with a cartilaginous skeleton and 5 to 7 gill slits on each side of its head.
  "The straunge fishe is in length xvij. foote and iij. foote broad, and in compas about the bodie vj. foote; and is round snowted, short headdid, hauing iij. rankes of teeth on either iawe, …. Also it hath v. gills of eache side of the head, shoing white. Ther is no proper name for it that I know, but that sertayne men of Captayne Haukinses doth call it a sharke."
• (uncountable) Flesh of this animal, consumed as food.
• (paleontology, loosely) Any fish of the class Chondrichthyes, especially an extinct shark-like holocephalian.
  "Cladoselache, a well-preserved Devonian shark fossil from Ohio. Here the cartilages and some muscle tissues are preserved intact"
• (countable) A noctuid moth of species Cucullia umbratica.

verb

• (intransitive, rare) To fish for sharks.
• (UK, university slang, mildly derogatory) Of a university student who is not a fresher (first-year undergraduate), and especially towards the start of the academic year:
• (UK, university slang, mildly derogatory) Of a university student who is not a fresher (first-year undergraduate), and especially towards the start of the academic year:

noun

• (informal, derogatory) A sleazy and amoral lawyer.
• (informal, derogatory) An ambulance chaser.
• (informal) A relentless and resolute person or group, especially in business.
  "In the event they lacked a proper midfield bolt, with Toni Kroos and Sami Khedira huffing around in pursuit of the whizzing green machine. The centre-backs looked flustered, left to deal with three on two as Mexico broke. Löw’s 4-2-3-1 seemed antiquated and creaky, with the old World Cup shark Thomas Müller flat-footed in a wide position."
• A person that excels in a particular field.

verb

• (obsolete) To steal or obtain through fraud.
• (obsolete, intransitive) To play the petty thief; to practice fraud or trickery; to swindle.
  "Neither sharks for a cup or a reckoning."
• (obsolete, intransitive) To live by shifts and stratagems.
  "Ah Captaine, lay not all the fault upon Officers you know you can ſhark though you be out of action, witneſſe Montague."