Definition from Wiktionary, the free dictionary
sharper (plural sharpers)
- (dated) a swindler; a cheat; a professional gambler who makes his living by cheating.
- 1766, Tobias Smollett, Travels through France and Italy, Letter XXIX, 
- Our young gentlemen who go to Rome will do well to be upon their guard against a set of sharpers, (some of them of our own country,) who deal in pictures and antiques, and very often impose upon the uninformed stranger, by selling him trash, as the productions of the most celebrated artists.
- 1878, John Payne, Introduction, in François Villon, Poems, translated by John Payne, New York: Boni & Liveright, c. 1918, p. 33 
- […] in a twinkling the accomplished sharper changes the pitchers and pretending to examine the contents, asks the tapster what kind of wine he has given him […]
- 1882, W. S. Gilbert, "Emily, John, James, and I: A Derby Legend" in The "Bab" Ballads, Philadelphia: David McKay, publishing date not given, p. 275, 
- The Derby Day sun glittered gaily on cads, / On maidens with gamboge hair, / On sharpers and pickpockets, swindlers and pads— / (For I, with my harp, was there).
- 1766, Tobias Smollett, Travels through France and Italy, Letter XXIX,