oil

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of numerous mineral, vegetable, or synthetic substances or animal or vegetable fats that are generally slippery, combustible, viscous, liquid or liquefiable at room temperatures, soluble in various organic solvents such as ether but not in water, and used in a great variety of products, especially lubricants and fuels.
• noun Petroleum.
• noun A petroleum derivative, such as a machine oil or lubricant.
• noun A protective or cosmetic liquid applied to the skin or hair.
• noun Oil paint.
• noun A painting done in oil paint.
• transitive verb To lubricate, supply, cover, or polish with oil.
• idiom (hand/palm) To bribe.
• idiom (hand/palm) To give a tip to.

from The Century Dictionary.

• In chem., a termination denoting an ether derived from a phenol: as, anisoïl (formerly called anisol).
• To smear or rub over with oil; prepare for use by the application of oil: as, to oil a rag; oiled paper or silk.
• To anoint with oil.
• To render smooth by the application of oil; lubricate: as, to oil machinery; hence, figuratively, to render oily and bland; make smooth and pleasing.
• to make it water-proof, as in China, Japan, etc., where oiled paper is extensively used for umbrellas, water-pails, lanterns, rain-clothes, etc.
• noun Indian geranium or palmarosa oil (formerly called Turkish geranium-oil), a fragrant essential oil distilled from the leaves of Andropogon Schœnanthus, used in perfumery. It comes from the Bombay Presidency in India.
• noun The general name for a class of bodies which have all or most of the following properties in common: they are neutral bodies having a more or less unctuous feel and viscous consistence, are liquid at ordinary temperatures, are lighter than water, and are insoluble in it, but dissolve in alcohol and more readily in ether, and take fire when heated in air, burning with a luminous smoky flame.
• noun Specifically Oil as used for burning in a lamp, to afford light: as, to burn the midnight oil (alluding to nocturnal study).
• noun An oil of indifferent scent from the Lebanon cedar.
• noun Oil of chrism, oil mixed with balsam, or with wine and aromatics, used at baptism, confirmation, coronation of sovereigns, etc.: also called chrism.
• noun Oil of the sick, oil used at the unction of the sick. See euchelaion and unction.
• noun Especially, in the Greek Church, oil which has been in contact with a relic or other sacred object, or has been taken from a church lamp.
• noun Oil of myrcia.
• noun Punishment with a birchen switch; a beating.

from the GNU version of the Collaborative International Dictionary of English.

• noun Any one of a great variety of unctuous combustible substances, more viscous than and not miscible with water; 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.
• noun etc. (Old Chem.), a complex oil obtained by the distillation of animal substances, as bones. See Bone oil, under Bone.
• noun (Chem.) See under Drying, and Essential.
• noun (Chem.) See under Ethereal.
• noun (Chem.) See under Fixed.
• noun (Zoöl.) a bag, cyst, or gland in animals, containing oil.
• noun (Zoöl.) any beetle of the genus Meloe and allied genera. When disturbed they emit from the joints of the legs a yellowish oily liquor. Some species possess vesicating properties, and are used instead of cantharides.
• noun (Mach.) a fixed box or reservoir, for lubricating a bearing; esp., the box for oil beneath the journal of a railway-car axle.
• noun See under Cake.
• noun a stopcock connected with an oil cup. See Oil cup.
• noun a painting made from such a paint.
• noun a cup, or small receptacle, connected with a bearing as a lubricator, and usually provided with a wick, wire, or adjustable valve for regulating the delivery of oil.
• noun a gas engine worked with the explosive vapor of petroleum.
• noun inflammable gas procured from oil, and used for lighting streets, houses, etc.
• noun (Zoöl.), (Bot.) A gland, in some plants, producing oil.
• noun a pale yellowish green, like oil.
• noun empyreumatic oil obtained by subjecting a brick soaked in oil to distillation at a high temperature, -- used by lapidaries as a vehicle for the emery by which stones and gems are sawn or cut.
• noun [Obs.] a nostrum made of calcined talc, and famous in the 17th century as a cosmetic.
• noun (Chem.) strong sulphuric acid; -- so called from its oily consistency and from its forming the vitriols or sulphates.
• noun Œnanthic ether. See under Œnanthic.
• noun Any kind of painting of which the pigments are originally ground in oil.