/ Dictionary / Index P penta-: Meaning and Definition of Find definitions for: penta- Pronunciation: [key] a combining form occurring in loanwords from Greek, meaning “five” (Pentateuch); on this model, used in the formation of compound words (pentavalent). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. pent pentachloronitrobenzene Related Content Daily Word Quiz: alacrity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language