/ Dictionary / Index E Einstein theory: Meaning and Definition of Find definitions for: Ein'stein the"ory Pronunciation: [key] — Physics. Physics. relativity (def. 2). Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Einstein's photoelectric equation Einthoven Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language