The definition of burn the midnight oil is:
(idiom) to go to bed very late and wake up very early to do a lot of work
Myriam always burns the midnight oil because she doesn’t plan very well, and has to do all of her work at the last minute.
Rachel burned the midnight oil because she had a presentation to give to her boss.
A: You look terrible, what happened?
B: I’m burning the midnight oil to try and finish my assignment for tomorrow.
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