Any one of a great variety of unctuous combustible substances,
   not miscible with water; as, olive oil, whale oil, rock oil, etc. They
   are of animal, vegetable, or mineral origin and of varied composition,
   and they are variously used for food, for solvents, for anointing,
   lubrication, illumination, etc. By extension, any substance of an oily
   consistency; as, oil of vitriol.