get on to one . get on to one {v. phr.} To figure someone out; understand what someone else is up to. The FBI is on to Jim's secret trading with the enemy. Categories: add yours {v. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2025 To section: G Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Add my comment