Chest-thumping churchgoer / religious donor who loudly proclaims his or her righteousness based solely on their Sunday attendance / offering. Tend to think they can get away with being braggardly arrogant self-important arseholes because they actually spend an hour or two in / a few bucks on church every week. They tend to cover their auto bumpers and SUV backglass with stickers alluding to Jesus, quote Biblical scripture completely out of context, and privately pleasure themselves to kiddie porn while chiding anybody who dares mention anything sexual in public.
The jagoff who cut you off coming out of the church parking lot - you know, the one in the $49 polyester suit jacket who flipped you off - this past Sunday morning is a McChristian.
One whose religion solely consists of celebrating commercialized Christian holidays. Synonym: commercialized Christian.
To a McChristian Easter means bunnies and colored eggs and Christmas means gifts, colored lights, and elves.