Green’s Dictionary of Slang

1. underhand, cheating.

1605		Marston Dutch Curtezan I i: Nay, be not jaw-falne, my most sharking Mulligrub.
1608		Dekker Belman of London H3: A crue of Sharking companions.
1650		A dialogue between Mistris Macquerella [etc] n.p.: What Saint is she / That keeps a shop of Brothelrie / Harbours the sharking Lawyer for his pence.
1659		Greene & Lodge Lady Alimony V iii: You shall play no more the sharking foist with me, you fumbling Fidler you.
1663		A. Cowley Cutter of Coleman-street (1721) 744: The Persons [...] Cutter, a merry, sharking fellow about the Town.
1751		Smollett Peregrine Pickle (1964) 179: He desired Mr. Jolter to keep his pupils out of the clutches of those sharking priests who lie in wait to make converts of all young strangers.
1760		C. Johnston Chrysal I 19: [I] entered into every project which my brain could invent [...] making my fortune a prey to every sharking projector who flattered my vanity with promises of success.
1821–6		‘Bill Truck’ Man o’ War’s Man (1843) 260: Your d—d Scotch and Irish sharking rascals.
1822		(con. early 17C) W. Scott Fortunes of Nigel II 114: The rest stood by and backed him, and especially the sharking Frenchman.

2. (W.I., Nevis) greedy, gluttonous.

1996

Allsopp Dict. Carib. Eng. Usage.