/ Dictionary / Index P planar: Meaning and Definition of Find definitions for: pla•nar Pronunciation: (plā'nur), [key] — adj. of or pertaining to a geometric plane. flat or level. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: planar (Thesaurus) plan planarian Related Content Daily Word Quiz: inutiae Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language