/ Dictionary / Index P plain clothes: Meaning and Definition of Find definitions for: plain' clothes' Pronunciation: [key] clothing other than one's uniform, esp. civilian clothes worn on duty by a police officer. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. plainchant plainclothesman Related Content Daily Word Quiz: fidelity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language