'Parfocal' definitions:
Definition of 'Parfocal'
From: GCIDE
- Parfocal \Par*fo"cal\, a. [Pari- + focal.] (Opt.) With the lower focal points all in the same plane; -- said of sets of eyepieces so mounted that they may be interchanged without varying the focus of the instrument (as a microscope or telescope) with which they are used. "the convenience of a microscope with parfocal objective lenses" [Webster 1913 Suppl.] Parforn