/ Dictionary / Index P Poisson's ratio: Meaning and Definition of Find definitions for: Poisson's' ra'tio Pronunciation: [key] — Physics. Physics. the ratio, in an elastic body under longitudinal stress, of the transverse strain to the longitudinal strain. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Poisson distribution Poitiers 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