liturgy

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A prescribed form or set of forms for public religious worship.
2. n. Christianity The sacrament of the Eucharist.

Century Dictionary and Cyclopedia

1. n. In ancient Greece, particularly at Athens, a form of personal service to the state which citizens possessing property to a certain amount were bound, when called upon, to perform at their own cost. These liturgies were ordinary, including the presentation of dramatic performances, musical and poetic contests, etc., the celebration of some festivals, and other public functions entailing expense upon the incumbent; or extraordinary, as the fitting-out of a trireme in case of war.
2. n. A form or method of conducting public worship; an appointed form for the words and acts used in the rites and ceremonies of the Christian church. The word denotes especially an appointed form for the holy communion, the hours or daily prayer, litanies, baptism, confirmation, marriage, burial, penance, visitation and unction of the sick or dying, ordinations, and other offices such as are contained in the Missal, Breviary, Ritual, Pontifical, Euchologion, Horologion, etc., of the Roman Catholic and the Greek Church, or united in one volume in the Anglican Book of Common Prayer. Liturgies seem to have originated partly in the inheritance or adoption of Jewish forms of worship and their adaptation to Christian purposes. The Book of Psalms, especially as containing inspired prayers, praises, thanksgivings, etc., furnished a large amount of liturgical material. On the other hand, the forms given by Christ, such as the Lord's Prayer, the words of institution in the eucharist, the baptismal formula, etc., became centers of development for the new and distinctively Christian parts of the offices.
3. n. Specifically, in liturgiology, and as the name most frequently used in the Greek Church, the form of service used in the celebration of the eucharist, or that service itself. In this last sense Latin and Roman Catholic writers generally prefer the word mass. An account of primitive Christian liturgical worship is given by Justin Martyr (in the middle of the second century a. d.), and this agrees with the Clementine Liturgy, a form referable to about a. d. 250, and so called because incorporated in the Apostolical Constitutions, a compilation attributed to St. Clement of Rome. Five great groups or families of liturgies are recognized, each of which can be referred to a single original liturgy represented by one or more direct derivatives still existing. They are:

Wiktionary

1. n. A predetermined or prescribed set of rituals that are performed, usually by a religion.
2. n. An official worship service of the Christian church.
3. n. liturgy.

GNU Webster's 1913

1. n. An established formula for public worship, or the entire ritual for public worship in a church which uses prescribed forms; a formulary for public prayer or devotion. In the Roman Catholic Church it includes all forms and services in any language, in any part of the world, for the celebration of Mass.

WordNet 3.0

1. n. a Christian sacrament commemorating the Last Supper by consecrating bread and wine
2. n. a rite or body of rites prescribed for public worship