/ Dictionary / Index E extension field: Meaning and Definition of Find definitions for: exten'sion field" Pronunciation: [key] a field that contains a given field as a subfield. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. extension courses extension ladder Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language