A thin layer of facial hair on the upper lip that looks like dirt was smeared over the persons face.
Look at AJs dirtstache, did he dive into a pile of shit?
by omgwtfywontudie (bill) October 23, 2007
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n. A layer of dirt on the upper lip and nose from riding dirt bikes/ATVs in a dusty region, particularly where the helmet does not cover the face.
I was riding behind you for miles, all that dust gave me the worst dirtstache!
by Milee B. June 2, 2013
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