1 [noncount] a : a thick, black liquid that comes from the ground and that is used in making various products (such as gasoline)
▪ The price of crude oil is expected to rise. ▪ drilling for oil — often used before another noun ▪ oil prices/companies/wells/refineries ▪ the oil industry ▪ The world's oil supplies/reserves are diminishing.
b : a type of oil that is used as a fuel to produce heat or light
▪ We heat our house with oil. ▪ heating oil ▪ an oil lamp
c : a type of oil that makes the different parts in an engine, machine, etc., run smoothly
▪ I asked the mechanic to check the oil. [=to make sure that there was enough oil to make the car engine run smoothly] ▪ A little bit of oil will help lubricate the chain. 2 [count, noncount] : a liquid substance that comes from a plant or animal, that contains fat, and that is used in cooking
▪ Add a little oil to the pan and stir-fry the onions. ▪ The dressing is made with oil, vinegar, and a pinch of herbs. — see also castor oil, coconut oil, cod-liver oil, corn oil, essential oil, linseed oil, olive oil, palm oil 3 [count, noncount] : a smooth substance that is used on the skin, hair, or body to make it soft or healthy
▪ scented bath oils 4 a oils [plural] : oil paints
▪ He works mostly in oils. [=he mostly uses oil paints]
b [count] : an oil painting
▪ The exhibit includes oils and watercolors. ▪ an oil on canvas