/ Dictionary / Index J J.C.S.: Meaning and Definition of Find definitions for: J.C.S. Pronunciation: [key] Joint Chiefs of Staff. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. JCL jct. Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language