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1. A benign (but disgusting) bacterial growth in the mouth that causes the tongue to become black and fuzzy. May spread to the teeth.

2. The grossest thing ever.

3. The side effect listed on the back of Pepto-Bismol packaging as "a harmless darkening of the tongue."

4. The #1 reason to never take Pepto-Bismol.
You: I woke up this morning with Black Hairy Tongue.
Friend: Ew. You shouldn't have taken pepto before bed!
by Kiwi27777 December 13, 2009
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