Slang for Weed.. back before weed prices were pretty much standard $25/50 - $30-60. You would haggle over what you were willing to pay for a bag. Hence the term. It is used when referring to weed over the phone.
(ring)(ring)...Hello, Yoh, what's up? Yougot any haggle man?
To try and convince someone to make whatever they are selling a lower price. They'll suggest a price, you'll suggest a lower one, and each of you keep on suggesting prices until you are willing to pay.