/ Dictionary / Index P peneplain: Meaning and Definition of Find definitions for: pe•ne•plain Pronunciation: (pē'nu-plān", pē"nu-plān'), [key] — n. Geol. an area reduced almost to a plain by erosion. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: peneplain (Thesaurus) Penelope penetrable Related Content Daily Word Quiz: belligerent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language