- burn the midnight oil
- burn the midnight oilFig. to stay up working, especially studying, late at night. (Alludes to working by the light of an oil lamp late in the night.) •
I have a big exam tomorrow so I'll be burning the midnight oil tonight.
•If you burn the midnight oil night after night, you'll probably become ill.
* * *{v. phr.} To study late at night. * /Exam time was near, and more and more pupils were burning the midnight oil./
Dictionary of American idioms. 2013.