A food that has barely been eaten and sitting on the top of a garbage. This is perfectly ok to eat as long as no one catch you. In "Seinfeld" George Castanza is seen eating a garbage floater by his girlfriends mom
Dude #1: I just had a soft pretzel i found in the garbage.
To be completly terrible at something, to not excel in any form. It may refer to someones skill at a certain subject, action, sport, or game. However it is often used to describe someones total lack of skill at games such as Madden 12, call of duty, or possibly mario cart. This phrase is also comparable to Ass Milk and Trash Sauce.