To scream at a group of people from a moving car. Followed by a quick getaway only if any member of the forementioned crowd has access to a car. This maneuver is preferrably executed at night to minimize the chances of your identity being known. Many times directed toward homeless tramps/skanks/posers, adolescents, and the elderly. The object simply being to scare the shit out of any unsuspecting person who must taste the brunt of your wrath. Does not have to be a coherent word - it can be any form of loud noise as well, such as an airhorn.
"We took a lap last night and did a blow-out to some people on graham (ave)."