odds-on odds-on {adj.}, {informal} Almost certain; almost sure; probable. Ed is the odds-on choice for class president, because he has good sense and good humor. Categories: add yours {adj.} {informal} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: O Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Discuss