Someone who has a "drug problem" who tends to speed down the street , going either forwards or backwards to make it to there most prized palace (the dealers house) , in order to get there drugs.
Speed basers tend to hit anything and everything in there path, including nearby mailboxes, children and even fellow speed based cars.
Teresa:Hey man im about a mile away , which means ill be there in 4 seconds flat
Dboy:say what!? that means your being a speed baser, chill the fuck out!