It is a colloquial term to describe a person who is quick to become inebriated relative to the amount of alcohol they have consumed. You could have searched this term and discovered the meaning yourself, you fool!

[ The world is definitely getting blurrier now. Exactly how long does he have until he passes out? Given how he feels right now... ]

Five more... minutes. Five more minutes until I pass out... by my estimate. I... Don't want to go though. When this ends I... have to acknowledge that they're gone again.