Boozescrounge 

Pronunciation: 'büzskraunj
Function: verb
Inflected Form(s): boozescrounged; boozescroung·ing
transitive verb
1 : To forage or scavenge for abandoned or neglected drinks in a bar, before the waitstaff collects them. Boozescroungers may consume drinks publicly--under pretense of legitimate purchase--or quickly, for concealment and faster alcohol absorption. Motivation for boozescrounging can be dipsomania, no money, principled conservation, kleptomania, fun, or any combination thereof.
2 : The act of any genuine boozehound (vagrant or employed) searching for, turning up, or begging for alcohol--or money solely for alcohol--from whatever source is available.
- boozescroung·er noun

1: Look at Rusty over there, boozescrounging the remnants of that big party of girls who just left: not one of them finished their drink, so he's really cashing in!
1: Jason's got that new well-paying job; why did he just boozescrounge that half-empty beer? He always did hate to see things go to waste, and old habits do die hard, I suppose.
2: Stopped at a busy intersection today, I noticed a refreshingly honest boozescrounger admitting on his sign, "I need a beer."

Boozescrounge by Knut C. Austerlitz January 2, 2009