/ Dictionary / Index E entrance pupil: Meaning and Definition of Find definitions for: en'trance pu"pil Pronunciation: [key] — Optics. Optics. the image of the aperture viewed from the objective of an optical system limiting the rays that enter the system. Cf. exit pupil. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. entrance entranceway 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