As opposed to pre-game where one drink alcohol before an event. Post game is meant for someone to drink alcohol after an event when they are already super drunk.
The feeling one gets in a particularly numbing book ending. Derived from the depressing empty feeling one usually gets at the end of Ender's Game the first time they finish it.
I just finished Mockingjay by Suzanne Collins. The book was excellent, but left me in an Ender's Game Daze.