that is . that is or that is to say I mean; that means; in other words. John is a New Yorker; that is, he lives in New York. Susan is a good student; that is to say, she gets good grades in school. No categories: add yours Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: T Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Discuss