Source : Webster's Revised Unabridged Dictionary (1913)
Sunday \Sun"day\, n. [AS. sunnand[ae]g; sunne, gen. sunnan, the
sun + d[ae]g day; akin to D. zondag, G. sonntag; -- so called
because this day was anciently dedicated to the sun, or to
its worship. See {Sun}, and {Day}.]
The first day of the week, -- consecrated among Christians to
rest from secular employments, and to religious worship; the
Christian Sabbath; the Lord's Day.
{Advent Sunday}, {Low Sunday}, {Passion Sunday}, etc. See
under {Advent}, {Low}, etc.
Syn: See {Sabbath}.
Advent \Ad`vent\, n. [L. adventus, fr. advenire, adventum: cf.
F. avent. See {Advene}.]
1. (Eccl.) The period including the four Sundays before
Christmas.
{Advent Sunday} (Eccl.), the first Sunday in the season of
Advent, being always the nearest Sunday to the feast of
St. Andrew (Now. 30). --Shipley.
2. The first or the expected second coming of Christ.
3. Coming; any important arrival; approach.
Death's dreadful advent. --Young.
Expecting still his advent home. --Tennyson.
Source : WordNet®
Advent Sunday
n : the first of the four Sundays during Advent