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2.
any military troop transport vehicle (including aircraft but not large ships)
mh-60 pilot: "all aboard the retard bus! come on you fuckers this thing won't be here forever"

soldier 1: "some dumbfuck got his helo shot down"
soldier 2: "typical, retard bus drivers never take care of passengers"
by DIABLtheLEGEND August 18, 2011
 
1.
Usually a school bus which is about
half the size of a regular school bus
which is used to transport the disabled/
handicapped along with those students who have discipline problems and other
issues where they are kept away from the
"normal" students.
"My son may not be a genius, but at least he doesn't take the retard bus
to school!"
by mvn64 November 21, 2004