Smokeless tobacco: Tobacco that is not smoked but used in another form such as chewing tobacco or snuff. Cancers of the oral cavity (mouth, lip, tongue) have been associated with the use of chewing tobacco as well as snuff. The tumors often arise at the site of placement of the tobacco.
Smokeless tobacco was formally classified as a "known human carcinogen" by the US government in 2000. See also: Tobacco.