/ Dictionary / Index P p.r.n.: Meaning and Definition of Find definitions for: p.r.n. Pronunciation: [key] (in prescriptions) as the occasion arises; as needed. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: prn (Thesaurus) PRM pro Related Content Daily Word Quiz: agitated Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language