1. An inflammable liquid, of fatty consistency and unctuous feel, which is insoluble in water, soluble or insoluble in alcohol, and freely soluble in ether. Oils are variously classified as animal, vegetable, and mineral according to their source (the mineral oils probably being of remote animal and vegetable origin); into fatty (fixed) and volatile oils; and into drying and nondrying (fatty) oils, the former gradually thickening when exposed to the air and finally drying to a varnish, the latter not drying but liable to become rancid on exposure. Many of the oils, both fixed and volatile, are used in medicine. For individual oils, see the specific names.
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