sit up with . sit up with {v. phr.} To be with; particularly to keep someone ill company. Mrs. Brown sat up with her sick husband all night in the hospital room. Categories: add yours {v. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: S Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Discuss