The word "fag bag" is used to define a single pound of marijuana.
As you may or may not know, a pound of marijuana is a ridicilious amount to have at one time. So, the term originates from all the faggot attention whores that try to look cool around your school when they shout out and brag about the absurd amounts of marijuana they consumed the day before.
It's typically used to make fun of those types of kids in a sarcastic high-pitched tone of voice.
Attention whore: "Oh, my God! I'm still so high from yesterday after smokin' so much weed yesterday!"
Person 1: "Dude, Naithen. You don't have to yell it, we're right next to you."
a boy who decides to act like an asshole by doing something that was stupid and uncalled for. one who tells you he'll come over and then doesnt, one who doesn't get the hint that you're interested, one who says youre good friends and you'll tell each other everything but then lies, one who doesnt return text messages, facebook messages and/or phone calls, one who dropped the 'i love you' bomb when it really wasn't called for.. but even after this you still talk to them.