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1.
The most acceptable forms of payment for the favor of being given a ride to any destination. Roughly translates to: money, weed, or sex (oral sex is also acceptable). Gifts should be given promptly and without hesitation.
Brian: Well, here we are.

Girl: Aw, well thanks for the ride Brian-

*she begins to exit the car*

Brian: Hey- hey, hey! Not so fast, its ass gas or grass in this car, bitch. And it seems I've got a full tank and plenty of the fine erb, so uhhh... *nods head, indicating genitals*
by BES the best July 03, 2006
152 43
 
2.
If someone is asking you for a ride and you don´t feel the need to give it away for nothing, it´s a good opportunity to ask for "ass, gas or grass".

Meaning you wish to take advantage of the situation by getting a good fuck, some bucks for the gas you´re gonna need or at least something to get a buzz from.

(Maybe one of you might describe it better, as I´m by no means a native speaker!)
"You wanna go to Mexico with me? Take a ride? Well, what´s your currency...
ass gas or grass ?
Nobody rides for free, you know?!"
by Fichtelschwein February 04, 2010
16 10