bonehead bonehead {n.}, {slang} An unusually dense or stupid person. John is such a bonehead — small wonder he flunks all of his courses. Categories: add yours {n.} {slang} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: B Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Discuss