Top definition
That extra ~1 gallon a car really has when the low-fuel light shows up on a car's dash. You think you're totally out of fuel but you actually have another gallon to's a courtesy gallon!
I have been driving on this courtesy gallon for a little too long; I should probably go to the gas station.

I was afraid about breaking down on the road but remembered I still had my courtesy gallon!
by colinstu April 17, 2011
Get the mug
Get a courtesy gallon mug for your barber Trump.