/ Dictionary / Index E extension tube: Meaning and Definition of Find definitions for: exten'sion tube" Pronunciation: [key] — Photog. Photog. any of a series of tubes of varying lengths placed between the lens and a camera body to facilitate closeup focusing. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. extension rule extensity Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language