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