When a man is having sex and their partner is riding them on top...at the moment of orgasm, he pulls out and shoots an enormous amount of semen wiping away any trace of tummy sweat, grime or greasy lubricant.
After waiting 6 months to consumate their relationship, Beto pulled out and gave his girlfriend an unforgettable Under Chassis Superwash.

When Felipe performed an Under Chassis Superwash on his girlfriend, he said the amount of semen splashing her stomach reminded him of a fire-hydrant after getting runover by a rookie driven squad car.
by PansaVerde August 14, 2010
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A car wash that's called a super wash
When mrs.porch got a SUPERWASH her car wasn't cleaned right
by Bobbbby hill August 3, 2017
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