/ Dictionary / Index D defensive back: Meaning and Definition of Find definitions for: defen'sive back' Pronunciation: [key] — Football. Football. a defender positioned off the line of scrimmage for the purpose of covering pass receivers and tackling runners who elude linemen and linebackers. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. defensive defensive medicine Related Content Daily Word Quiz: soporific Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language