What is Boycott?

Legal Definition
A boycott is an act of voluntarily abstaining from using, buying, or dealing with a person, organization, or country as an expression of protest, usually for social or political reasons. The purpose of a boycott is to inflict some economic loss on the target, or to indicate a moral outrage, to try to compel the target to alter an objectionable behavior.

Sometimes, a boycott can be a form of consumer activism, sometimes called moral purchasing. When a similar practice is legislated by a national government, it is known as a sanction.
-- Wikipedia
Legal Definition
A conspiracy formed and intended directly or, indirectly to prevent the carrying on of any lawful business or to injure the business of any one by wrongfully preventing those who would be customers from buying anything from or employing the representatives of said business, by threats, intimidation or other forcible means. Gray v. Building Trades Council, 91 Minn. 171, 97 N. W. 663, 63 In B. A. 753, 103 Am. St. Rep. 477; State v. Glidden, 55 Conn. 46, 8 Atl 890, 3 Am. St Rep. 23; In re Crump, 84 Va. 927, 6 S. B. 620, 10 Am, St Rep. 895; Oxley Stave Co. v. International Union (C. C.) 72 Fed. 699; Casey v. Typographical Union (C. C.) 45 Fed. 135, 12 L. R. A. 193; Davis v. Starrett, 97 Me. 568, 55 Atl. 516; Barr v. Essex Trades Council, 53 N. J. Eq. 101, 30 Atl. 881; Park v. Druggists' Ass'n, 175 N. Y. 1, 67 N. E. 136, 62 L It. A. 632, 96 Am. St. Rep. 578.
-- Black's Law Dictionary
Legal Definition
An attempt by persons acting in combination to coerce one to follow a prescribed line of conduct by compelling others to shun him in business. See 63 L. R. A. 753; also 90 Am. St. Rep. 451.
-- Ballentine's Law Dictionary