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