/ Dictionary / Index P psoralen: Meaning and Definition of Find definitions for: pso•ra•len Pronunciation: (sôr'u-lun, sōr'-), [key] — n. Pharm. a toxic substance, CHO, found in certain plants, including parsnips, used to increase the response to ultraviolet light in the treatment of severe cases of acne and psoriasis. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. psora psoriasis Related Content Daily Word Quiz: profiterole Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language