/ Dictionary / Index P periplasm: Meaning and Definition of Find definitions for: per•i•plasm Pronunciation: (per'u-plaz"um), [key] — n. an outer cytoplasmic layer that surrounds the oosphere in certain fungi. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. periphyton periproct Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language