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Meaning of parfocal

par•fo•cal

Pronunciation: (pär-fō'kul), [key]
— adj. Optics.
  1. of or pertaining to different eyepieces (of telescopes or microscopes) that all focus their images in the same plane, so that they can be interchanged without readjusting the instrument.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.