Parfocal
Pronunciation : Par*fo"cal
Part of Speech : a.
Definition : Defn: 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.
[Pari- + focal.] (Opt.)
Source : Webster's Unabridged Dictionary, 1913