/ Dictionary / Index K knucklehead: Meaning and Definition of Find definitions for: knuck•le•head Pronunciation: (nuk'ul-hed"), [key] — n. Informal. a stupid, bumbling, inept person. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: knucklehead (Thesaurus) knuckle-duster knuckle joint Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language