/ Dictionary / Index P plane trigonometry: Meaning and Definition of Find definitions for: plane' trigonom'etry Pronunciation: [key] — Math. Math. the branch of trigonometry dealing with plane triangles. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. plane tree planet-struck Related Content Daily Word Quiz: cygnet Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language