/ Dictionary / Index P PCNB: Meaning and Definition of Find definitions for: PCNB Pronunciation: [key] pentachloronitrobenzene. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. PCMCIA PCP Related Content Daily Word Quiz: pugilist Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language