/ Dictionary / Index C castellum: Meaning and Definition of Find definitions for: cas•tel•lum Pronunciation: (ka-stel'um), [key] — pl. cas•tel•li a small isolated fortress, or one of a series of such fortresses, of the ancient Romans. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Castellón de la Plana Castelnuovo-Tedesco Related Content Daily Word Quiz: illegible Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language