From The Art and Popular Culture Encyclopedia
Excommunication is an institutional act of religious censure used to deprive, suspend, or limit membership in a religious community or (as in the case of the Catholic Church) to restrict certain rights within it, such as the reception to Holy Communion. Some Protestants use the term disfellowship instead.
The word excommunication means putting a specific individual or group out of communion. In some religions, excommunication includes spiritual condemnation of the member or group. Excommunication may involve banishment, shunning, and shaming, depending on the religion, the offense that caused excommunication, or the rules or norms of the religious community. The grave act is often remedied by sincere penance, public recantation, sometimes through the Sacrament of Confession, piety, and/or through mortification of the flesh.