burn the midnight oil . burn the midnight oil {v. phr.} To study late at night. Exam time was near, and more and more pupils were burning the midnight oil. Categories: add yours study time {v. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: B Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Discuss