Real Dictionary

solidarity
uncountable noun: If a group of people show solidarity, they show support for each other or for another group, especially in political or international affairs.

solidarity in American English
combination or agreement of all elements or individuals, as of a group; complete unity, as of opinion, purpose, interest, or feeling
noun: a Polish organization of independent trade unions founded in 1980: outlawed by the government of Poland in 1982
noun: union or fellowship arising from common responsibilities and interests, as between members of a group or between classes, peoples, etc

solidarity in British English
noun: the organization of free trade unions in Poland: recognized in 1980; outlawed in 1982; legalized and led the new noncommunist government in 1989
noun: unity of interests, sympathies, etc, as among members of the same class