not all there not all there {adj. phr.} Not completely alert mentally; absentminded; not together. Bill is a wonderful guy but he is just not all there. Categories: add yours {adj. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: N Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Discuss