/ Dictionary / Index P principally: Meaning and Definition of Find definitions for: prin•ci•pal•ly Pronunciation: (prin'su-pu-lē, -sip-lē), [key] — adv. chiefly; mainly. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: principally (Thesaurus) principality principal parts 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