/ Dictionary / Index P phase space: Meaning and Definition of Find definitions for: phase' space" Pronunciation: [key] — Physics. Physics. a hypothetical space constructed so as to have as many coordinates as are necessary to define the state of a given substance or system. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. phase rule phase velocity Related Content Daily Word Quiz: frugal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language