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The brown fecal colour and flakes that appear around an anus.
When she bent over, Kyle could clearly see a ring of bumrust around her anus.
by jungletriad December 05, 2004
basically dried poop stuck on an anis
bye you rusty little bumcrack.
Orlando was giving it to Ficklestean in the bum, he yelled, "I can see your bum rust!"
by karl55655 November 09, 2007