What does "christmas" mean?

Christmas: An annual church festival (December 25) and in some States a legal holiday, in memory of the birth of Christ, often celebrated by a particular church service, and also by special gifts, greetings, and hospitality. Christmas box. (a) A box in which presents are deposited at Christmas. (b) A present or small gratuity given to young people and servants at Christmas; a Christmas gift. -- Christmas carol, a carol sung at, or suitable for, Christmas. -- Christmas day. Same as Christmas. -- Christmas eve, the evening before Christmas. -- Christmas fern (Bot.), an evergreen North American fern (Aspidium acrostichoides), which is much used for decoration in winter. -- Christmas flower, Christmas rose, the black hellebore, a poisonous plant of the buttercup family, which in Southern Europe often produces beautiful roselike flowers midwinter. -- Christmas tree, a small evergreen tree, set up indoors, to be decorated with bonbons, presents, etc., and illuminated on Christmas eve.