King James Dictionary 
AD'VENT, n. L. adventus, from advenio, of ad and venio, to come. See Find.
A coming appropriately the coming of our Savior, and in the calendar, it includes four sabbaths before Christmas, beginning of St. Andrew's Day, or on the sabbath next before or after it. It is intended as a season of devotion, with reference to the coming of Christ in the flesh, and his second coming to judge the world.
Holman Bible Dictionary 
Advent may also refer to the second coming or second advent of Christ. See Parousia; Second Coming.
Fred A. Grissom
Webster's Dictionary 
(1): (n.) The period including the four Sundays before Christmas.
(2): (n.) The first or the expected second coming of Christ.
(3): (n.) Coming; any important arrival; approach.
Hastings' Dictionary of the Bible 
ADVENT . See Parousia.
Hastings' Dictionary of the New Testament 
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
(Lat. adventus, sc. Redemptoris), signifies the coming of our Savior. The name is applied to the season (four weeks in the Roman, Lutheran, and English Churches, six weeks in the Greek Church) preceding Christmas. The origin of this festival as a Church ordinance is not clear. The first notice of it as such is found in the synod of Lerida (A.D. 524), at which marriages were interdicted from the beginning of Advent until Christmas. Caesarius of Aries (A.D. 542) has two sermons on Advent, fully implying its ecclesiastical celebration at that time. The four Sundays of Advent, as observed in the Romish Church and the Church of England, were probably introduced into the calendar by Gregory the Great. It was common from an early period to speak of the coming of Christ as fourfold: his "first coming in the flesh," his coming at the hour of death to receive his faithful followers (according to the expressions used by St. John), his coming at the fall of Jerusalem ( Matthew 24:30), and at the day of judgment. According to this fourfold view of the Advent, the "gospels" were chosen for the four Sundays, as was settled in the Western Church by the Homilarium of Charlemagne.
The festival of Advent is intended to accord in spirit with the object celebrated. As mankind were once called upon to prepare themselves for the personal coming of Christ, so, according to the idea that the ecclesiastical year should represent the life of the founder of the Church, Christians are exhorted during this festival to look for a spiritual advent of Christ. The time of the year, when the shortening days are hastening toward the solstice — which almost coincides with the festival of the Nativity — is thought to harmonize with the strain of sentiment proper during Advent. In opposition, possibly, to heathen festivals, observed by ancient Romans and Germans, which took place at the same season, the Roman Church ordained that the four weeks of Advent should be kept as a time of penitence, according to the words of Christ, "Repent, for the kingdom of heaven is at hand." During these weeks, therefore, public amusements; marriage festivities, and dancing are prohibited, fasts are appointed, and sombre garments used in religious ceremonies. The Protestant Church in Germany abstains from public recreations and celebrations of marriage during Advent, but fasting is not enjoined. The Church of England and Protestant Episcopal Church observe Advent, but do not prescribe fasts. Advent begins on the first Sunday after November 26, i.e. the Sunday nearest St. Andrew ’ s Day. In the sixth century, the Eastern and Western Churches (following the Nestorians) made Advent the beginning of the Church year instead of Easter. (See Bingham, Orig. Eccl. bk. 21, ch. 2, § 4; Procter, On Common Prayer, p. 268.) (See Christmas).
On the general subject of the appropriateness of the time of Christ ’ s advent, see the treatises, in Latin, of Austrin (Lond. 1835); Bock (Regiom. 1756, 1761); Faber (Kil. 1770, Jen. 1772); Hagen (Clausth. 1741); Quandt (Regiom. 1724); Ravius (Feft. 1673); Unger (Neap. 1779); Walch (Jen. 1738); Meyer (Kil. 1695); Scharbau (in his Obs. Sacr. 2, 395 sq.). On the state of the world at the time, Heilmann (Rint. 1755); Knapp (Hal. 1757). On the closing of the temple of Janus at his birth, Masson (Rotterd. 1700); and in German, Gedicke (in his Verm. Schrit, Berl. 1801, p. 188-200). (See Nativity).
In addition to what has already been given on this subject, it may be proper to add the directions of the various councils respecting the observance of the feast. A canon of the Council of Macon (A.D. 581) enjoins that from the Feast of St. Martin (Nov. 11) to the Nativity there be fasting on Monday, Wednesday, and Friday of each week, and that the canons be then read; also that the sacrifices be offered in the Quadragesimal order. In the second Council of Tours (567), the fast of three days in the week is ordered for the months of September, October, and November, and from Dec. 1 to. the Nativity every day. But this is for monks oily. It seems, from all that is certainly known, that Advent took its place among. Church seasons only in the latter part of the 6th century. Once established as one of the great festivals, it was felt that its dignity demanded a season of preparation. Originally left to the discretion of the faithful, the number of days or weeks to be set apart was eventually defined by rule, and at first, it seems, in the churches of Gaul. Yet the same rule did not everywhere prevail, for the oldest Gallican sacramentary shows .three Sundays in Advent, and the Gothic-Gallican only two. But the rule that the term of preparation should be a quadragesima, to commence after the Feast of St. Martin, implies six Sundays. This rule-not enacted, but re-enforced, by the Canon of Macon (581)-obtained in other churches, as appears from the fact that the Ambrosian (or Milan) and Mozarabic (or Spanish) Ordo shows six missae implying that number of Sundays, and the same rule was observed in some of the Gallican churches. The rule-not of Advent, but of this quadragesima-is first met with in the diocese of Tours. The observance of the Quadragesima Apostolorum and Quadragesinua S. Philippi (ii the. Greek calendar Nov. 14) is enjoined upon monks by Nicephorus, patriarch of Constantinople' (806). The Church of Rome, under Gregory, at the close of the 6th century, received the season of preparation as an ecclesiastical rule, restricted in its proper sense to the four Sundays before the Nativity, and this became the general rule for the Western Church throughout the 8th century and later. The Sacramentary of Gelasius, a Lectionary written for Charlemagne by Paul the Deacon, and other older works, all give five Sundays. This seeming discrepancy is easily explained, since the fifth Sunday before the Nativity was not considered as itself a Sunday in Advent, but as the preparation for Advent.
After the pattern of the Lenten fast, Advent was marked as a season of mourning in the public services of the Church. The custom of omitting the Gloria in Excelsis, and also: the Te Deum and Ite Missa Est, and of laying aside the dalmatic and subdeacon's vestment, was coming into use during the 8th century. The Benedictine monks retained the Te Deum in Advent as in Lent, alleging the rule of their founder. The Alleluia also, and the sequences, as also the hymns, were omitted, but not in all churches. In some churches the Miserere (Psalm li) and other mournful psalms were added to or substituted for the ordinary psalms. For lessons, Isaiah was read all through, beginning on Advent Sunday. When that was finished, the twelve minor prophets followed, or readings from the fathers, especially the epistles of pope Leo on the incarnation and sermons of St. Augustine.
In the Greek Church the .season of preparation for the Nativity is of late introduction.- No notice of it occurs in the liturgical works of Theodore Studites, though the forty days fast of St. Philip was enjoined (upon monks) by Nicephorus. This forty days' fast, beginning Nov. 14, is now the rule of the Greek Church. In the separated churches f. the East no trace appears, within our period, of an Advent season, unless we except the existing Nestorian or Chaldsean rule, in which the liturgical year begins with four Sundays of Annunciation before the Nativity. The Armenian Church, refusing to accept Dec. 25 as the Feast of the Nativity, and adhering to the more ancient sense of the Feast of Epiphany as including the birth of Christ, prepares for this high festival (Jan. 6) by a fast of fifty days, beginning Nov. 17.