1. A hairy tongue which is a benign side effect of some antibiotics; dark overgrowth of the papillae of the tongue.
2. A benign hairy condition of the tongue characterized by hypertrophy of the filiform papillae, giving the dorsum of the tongue a furry appearance.

The color of the elongated papillae varies from yellowish white to brown or black (black hairy tongue), depending upon staining by substances; such as, tobacco, foods, or drugs.