Drunk post, inserted into any thread usually having nothing to do with the context of the post. Usually raunchy or irritating.
Josh had a couple too many last night and used chrisism to annoy half of the board.
A verbal thought or question spewed forth without any thought given to it.
He ordered the "make your own pasta" and then handed the menu back to the waitress without picking a pasta or a sauce. What a Chrisism!