Christ·mas noun, often attributive \ˈkris-məs\
: a Christian holiday that is celebrated on December 25 in honor of the birth of Jesus Christ or the period of time that comes before and after this holiday
1: a Christian feast on December 25 or among some Eastern Orthodox Christians on January 7 that commemorates the birth of Christ and is usually observed as a legal holiday
2: Christmastide
—Merriam-Webster Dictionary