What does Black Hairy Tongue mean?

Black Hairy Tongue meaning in Urban Dictionary

1. A benign (but disgusting) bacterial growth in the lips which causes the tongue to become black colored and fuzzy. Might distribute on teeth.2. The grossest thing ever.3. The side impact listed on the rear of Pepto-Bismol packaging as "a harmless darkening of this tongue."4. The #1 explanation to never take Pepto-Bismol.