Burn the midnight oil is an idiom that means to work late into the night. There are several synonyms for this phrase such as, to work overtime, to work late, to burn the candle at both ends, to pull an all-nighter, to work around the clock, to work until the wee hours of the morning, to work into the night, to work after hours, to work the graveyard shift, to work until dawn, and to work through the night. These phrases all convey the idea of working late and sacrificing rest in order to get the job done. They are useful expressions to use in a variety of contexts such as work, school, and personal projects.