Etimology
From Middle English oyle, oile (“olive oil”), borrowed from Anglo-Norman olie, from Latin oleum (“oil, olive oil”), from Ancient Greek ἔλαιον (élaion, “olive oil”), from ἐλαία (elaía, “olive”). Compare Proto-Slavic *lojь. More at olive. Doublet of oleum. Supplanted Middle English ele (“oil”), from Old English ele (“oil”), also from Latin.
noun
oil (countable and uncountable, plural oils)
Liquid fat.
Petroleum-based liquid used as fuel or lubricant.
Petroleum.
(countable) An oil painting.
(painting) Oil paint.
(attributive) Containing oil, conveying oil; intended for or capable of containing oil.
Examples
The dawn of the oil age was fairly recent. Although the stuff was used to waterproof boats in the Middle East 6,000 years ago, extracting it in earnest began only in 1859 after an oil strike in Pennsylvania. The first barrels of crude fetched $18 . It was used to make kerosene, the main fuel for artificial lighting after overfishing led to a shortage of whale blubber.
Yet, in another way, I was unable to put Picasso's oils in the same class as Cezanne's, or even as Renoir's.
I prefer to paint in oil
oil barrel; oil pipe
Such a vehicle is made by taking any old barrel and through each head of the barrel an inch hole is bored, and an iron bar is driven through, leaving the ends projecting about eight inches.
Etimology
From Middle English oilen, oylen, from the noun (see above).
verb
oil (third-person singular simple present oils, present participle oiling, simple past and past participle oiled)
(transitive) To lubricate with oil.
(transitive) To grease with oil for cooking.
Examples
Before they went to see Glinda, however, they were taken to a room of the Castle, where Dorothy washed her face and combed her hair, and the Lion shook the dust out of his mane, and the Scarecrow patted himself into his best shape, and the Woodman polished his tin and oiled his joints.
The face which emerged was not reassuring. […]. He was not a mongol but there was a deficiency of a sort there, and it was not made more pretty by a latter-day hair cut which involved eccentrically long elf-locks and oiled black curls.