Tobacco pouch keratosis: A white, wrinkled change of the mucosa in the mandibular buccal vestibule secondary to the use of chewing tobacco. This lesion consists of a thick brownish black encrustation on the buccal mucosa at the site of placement of the buccal quid. It is often seen among heavily addicted betel quid chewers. It could be scraped off with a piece of gauze; it regresses spontaneously; more frequently when the habit is discontinued.