Definition of Excommunication
In old English law, a sentence of censure pronounced by one of the spiritual courts for offenses falling under ecclesiastical cognizance. It is described as two-fold: (1) The lesser excommunication, which is an ecclesiastical censure, excluding the party from the sacraments; (2) the greater, which excludes him from the company of all Christians. Formerly, too, an excommunicated man was under various civil disabilities. He could not serve upon juries or be a witness in any court; neither could he bring an action to recover lands or money due to him. These penalties were abolished in England by St. 53 Geo. Ill, c. 127.
That's the definition of Excommunication in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.