Santastic: (adj) portmanteau of Santa and Fantastic; used to describe something that exudes Christmas spirit and brings joy, happiness or brightness to someone else in the manner of Santa Claus bringing smiles to children.
Go on, use it in a sentence and add it to your vocabulary. Example: "The Christmas movie Elf is Santastic!" "My friend Lisa is filled with randsanity or maybe just Dewfeine. She went around town all day on Saturday in a wacky holiday sweater and a santa hat. She's so Santastic!"
Wishing you a very Santastic holiday season!