When you wake up with a hangover, but then do it all over again (see hair of the dog that bit you). The resulting catastrophe the NEXT day is the ever-dreaded re-hangover.
EXAMPLE 1- After two nights of drinking, Lynda's re-hangover was so bad that she actually considered alcoholism as an alternative to sobering up.
EXAMPLE 2- Dude #1: "I can't believe you went to your company Christmas party last night. Not after all the drinking we did the night before, man"
Dude #2: "I was so re-hungover this morning, I could barely hold my dick to take a leak."