Money, usually a significant amount to be used in a relatively short amount of time.
"We're about to go buy some stuff. He's got some flowage."
When someone cool sponsors party favors to a number of other cool people and even mizes, usually by buying a keg of beer or passing around endless bong hits.
When Bob hangs out there's always flowage and he scores the fine green, we should get him a bong for his birthday next week.