It means participant, united, glued, affiliated. That is part of a society or an association, member. Gathered, twinned, enrolled, incorporated.
1º_ As a noun is who belongs to a commercial association. See partner . 2º_ As an adjective qualifies the previous one, in addition to any person who accompanies or collaborates with others in a common task, or something that is supportive of another. 3º_ Participle of the verb associate .