It means rejection, exclusion, separation, isolation and boycott. It is the action of blocking in certain activities someone wants that force to that change of attitude. There may be commercial or supply boycott.
The origin of the word is in the surname of Irish farms Manager Charles Cunningham Boycott, which was suffocating to tenants with high taxes at the end of the 19th century; so the Irish Land League, grouping them created a method of pressure consisting in refusing to deal with it until it reduced these taxes. The times coined the term to refer to this case to define the new method of peaceful protest.
BOYCOTT: Exclusion of all action commercial or social that is imposed to a guy.