xmas(n = noun.time) christmas, christmas day, dec 25 - a Christian holiday celebrating the birth of Christ; a quarter day in England, Wales, and Ireland;
is a kind of quarter day, feast day, fete day, holy day of obligation, legal holiday, national holiday, public holiday
is a part of dec, december

xmas, n. colloq. = CHRISTMAS.

Etymology:
abbr., with X for the initial chi of Gk Khristos Christ