Sharp practice is a pejorative phrase used by lawyers to describe sneaky or cunning behavior that is technically within the rules of the law but borders on being unethical

Legal ethics

Legal ethics encompasses an ethical code governing the conduct of persons engaged in the practice of law and persons more generally in the legal sector.-In the United States:...

. An example of sharp practice would be for one party to "take advantage of a clear oversight by the opposite party in a proceeding." According to one Canadian court of appeal judgement, judges should not accuse counsel of sharp practice lightly and should generally not make such an accusation based solely on written submissions.