“Excommunication” means expulsion from communion

1. Jewish excommunication. --The Jewish system of excommunication was threefold. The twenty-four offences for which it was inflicted are various, and range in heinousness from the offence of keeping a fierce dog to that of taking God's name in vain. The offender was first cited to appear in court; and if he refused to appear or to make amends, his sentence was pronounced. The term of this punishment was thirty days; and it was extended to a second and to a third thirty days when necessary. If at the end of that time the offended was still contumacious, he was subjected to the second excommunication. Severer penalties were now attached. The sentence was delivered by a court of ten, and was accompanied by a solemn malediction. The third excommunication was an entire cutting off from the congregation. The punishment of excommunication is not appointed by the law of Moses; it is founded on the natural right of self-protection which all societies enjoy. In the New Testament, Jewish excommunication is brought prominently before us in the case of the man that was born blind. (John 9:1) ... In (Luke 6:22) it has been thought that our Lord referred specifically to the three forms of Jewish excommunication: "Blessed are ye when men shall hate you, and when they shall separate you from their company, and shall reproach you, and cast out your name as evil, for the Son of man's sake."
2. Christian excommunication. --Excommunication, as exercised by the Christian Church, was instituted by our Lord, (Matthew 18:15,18) and it was practiced and commanded by St. Paul (1 Corinthians 5:11; 1 Timothy 1:20; Titus 3:10) Int he epistles we find St. Paul frequently claiming the right to exercise discipline over his converts; comp. (2 Corinthians 1:23; 13:10) We find, (1) that it is a spiritual penalty, involving no temporal punishment, except accidentally; (2) that it consists in separation from the communion of the Church; (3) that its object is the good of the sufferer, (1 Corinthians 5:5) and the protection of the sound members of the Church, (2 Timothy 3:17) (4) that its subjects are those who are guilty of heresy, (1 Timothy 1:20) or gross immorality, (1 Corinthians 5:1) (5) that it is inflicted by the authority of the Church at large, (Matthew 18:18) wielded by the highest ecclesiastical officer, (1 Corinthians 5:3; Titus 3:10) (6) that this officer's sentence is promulgated by the congregation to which the offender belongs, (1 Corinthians 5:4) in defence to his superior judgment and command, (2 Corinthians 2:9) and in spite of any opposition on the part of a minority, (2 Corinthians 2:6) (7) that the exclusion may be of indefinite duration, or for a period; (8) that its duration may be abridged at the discretion and by the indulgence of the person who has imposed the penalty, (2 Corinthians 2:8) (9) that penitence is the condition on which restoration to communion is granted, (2 Corinthians 2:8) (10) that the sentence is to be publicly reversed as it was publicly promulgated. (2 Corinthians 2:10)