Accidentally farting whilst having your arsehole rimmed.
I was licking hard on Neil's hoop when suddenly he let out a dirty cloud. I could taste what he had for dinner.
by Squibby_ January 31, 2011
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An ominous looking cloud, generally dark in color, a sure sign of an approaching storm
Al: Great Scott! Victor, is that a dirty cloud I spy?

Victor: Indeed it is, we should seek shelter immediately.
by Mr. Ninja Man August 10, 2009
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