out to lunch . out to lunch {adj.}, {slang}, {informal} 1. Gone for the midday meal. 2. Inattentive; daydreaming; inefficient; stupid. Neil Bender is just out to lunch today. Categories: add yours {adj.} {informal} {slang} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2025 To section: O Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Post my comment