/ Dictionary / Index E expert witness: Meaning and Definition of Find definitions for: ex'pert wit'ness Pronunciation: [key] a person, as a physician, who provides testimony at a legal proceeding in the form of professional opinions. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. expert system expiable Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language