Crafty or deceitful dealings, especially in business. For example, That firm's known for its sharp practice, so I'd rather not deal with them. This expression, first recorded in 1836, uses sharp in the combined sense of “mentally acute” and “cutting.”
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use sharp practice in a sentence
His acquaintance among the sharp practice attorneys had been lately increasing, and he was soon almost fully employed by them.The Chronicles of Crime or The New Newgate Calendar. v. 1/2 | Camden Pelham
We are regarded as interlopers who have been guilty of sharp practice.The Squire's Daughter | Silas K(itto) Hocking
This was considered a bit of "sharp practice" by the Demerarians, but perhaps turned out for the best.The West Indies and the Spanish Main  | James Rodway
sharp practice amongst respectable firms is also very common, and verbal agreements are less trustworthy than in England.Town Life in Australia | R. E. N. (Richard) Twopeny
Over-reaching, or, what we Americans call 'sharp practice,' he had no patience with whatever.Dr. John McLoughlin, the Father of Oregon | Frederick Van Voorhies Holman