/ Dictionary / Index P principal sum: Meaning and Definition of Find definitions for: prin'cipal sum' Pronunciation: [key] — Insurance. Insurance. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. principal series principal value Related Content Daily Word Quiz: deleterious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language