1. slang A hangover. Well, if you don't remember last night at the bar at all, I'm not surprised you have barrel fever today!

2. slang The state of being intoxicated or drunk. Well, I must have had barrel fever last night if I got up and did karaoke at the bar!

3. slang A case of delirium tremens (a state of physical distress due to alcohol withdrawal, especially after chronic or heavy use). If Pop just stops drinking without being monitored by doctors, he might develop barrel fever.