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1.
when a person climbs on top of a mustang and shits all over it and leaves chunks of corn and other fecal matter all over the hood, windows, and trunk.
Skyler climbed up on that stang and took a shit all over it and now its a poostang.
by wooker G October 07, 2007
 
2.
Poostang is a way to insult ford mustangs. A very commonly used term in the f-body community (camaro/trans am).

Also used by any driver after a race that just wrecked a mustang.
Hey dan, did you see that dumbass in that slow poostang "try" to race me?
by j pags March 23, 2009