mask [Fr, masque] , 1. v., to obscure, as in symptomatic treatment that may conceal the development of a disease. 2. v., to cover, as does a skin-toned cosmetic that may hide a pigmented nevus. 3. n., a cover worn over the nose and mouth to prevent inhalation of toxic or irritating materials, to control delivery of oxygen or anesthetic gas, or (by medical personnel) to shield a patient during aseptic procedures from pathogenic organisms normally exhaled from the respiratory tract. Surgical masks are worn by workers to help control the operating room environment during a patient procedure.
