It is a bus that mentally disabled people are transported on. The white bus is commonly seen full of people driving around Glasgow. It is sometimes the object of ridicule, for example, it can be used to insult someone.
1. "Look, there's a white bus coming up the road. That's a shame."

2."Shut it, you get the white bus to school."
*On seeing a white bus driving away*: "Look Josh, you missed your bus."

by Michael-0 February 23, 2007
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To vomit-more precisely to vomit into a toilet.
After consuming the most of a case of beer, Chad ran to the bathromm where john caught him driving the white bus.
by mj_oblio June 17, 2004
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Puking up your guts into the toilet bowl while holding on to the rim with both hands to prevent yourself from falling in, while the room spins around and around.
After the party last night I went home and started driving the big white bus.
by PeeBee February 17, 2004
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