Those people not happy with the Christmas Season, not being with family, or simply over it, thus turning themselves into the Grinch and waiting for the holidays to end
Joe: Dude, whats wrong with Rob? Its almost Christmas!
Rob: Joe, he has to work this year and will be alone, He's only celebrating Grinchmas
Loosely based on the holiday of Festivus, Grinchmas is a time to degrade and embarrass all and any who you deem deserving. Grinchmas is celebrated from midnight of Christmas Eve to 5:45 AM of Christmas morning. Social networks are commonly used to spit grinchmas venom far and wide.
Damn, did you see what was said about Mark Dorsey during Grinchmas? Poor guy's feelings must really be hurt.