When you just can't wait until Friday to start your weekend partying, and end up getting "Thursdrunk". Normally involves calling in sick to work or school Friday morning, or at least going in with a 'slight' hangover.
Robert has had such a rough week that he's not going to be able to wait until the weekend to party, so I'm sure he'll be Thursdrunk tonight, and be calling in sick to work on Friday morning.