n. The act of invoking or calling in prayer; the form or act of summoning or inviting presence or aid: as, invocation of the Muses.n. In law, a judicial call, demand, or order: as, the invocation of papers or evidence into a court.n. Eccles.: An invoking of the blessing of God upon any undertaking; especially, an opening prayer in a public service invoking divine blessing upon it; specifically, the words “In nomine Patris, et Filii, et Spiritus Sancti. Amen,” “In the name of the Father, and of the Son, and of the Holy Ghost. Amen,” used at the beginning of the Roman mass, before sermons in many Anglican churches, and on other occasions.n. The third part of the prayer of consecration in the communion office of the American Book of Common Prayer, in the Scottish office of 1764 (from which that prayer is derived), and in the Nonjurors' office of 1718, on which, as well as on earlier Scottish and English offices and ancient Oriental liturgies, the Scottish office of 1764 is based.n. In the Roman Catholic and Anglican litanies, one of the petitions addressed to God in each person and in Trinity, and to the saints.