/ Dictionary / Index T thunderhead: Meaning and Definition of Find definitions for: thun•der•head Pronunciation: (thun'dur-hed"), [key] — n. Meteorol. incus (def. 2). cumulonimbus. the upper portion of a cumulus cloud characterized by dense, sharply defined, cauliflowerlike upper parts and sometimes by great verticality. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: thunderhead (Thesaurus) thunder egg thundering Related Content Daily Word Quiz: agitated Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language