Dioptre

1 definition found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Dioptre \Di*op"tre\, n. [F. See 2d {Dioptric}.] (Optics)
     A unit employed by oculists in numbering glasses according to
     the metric system; a refractive power equal to that of a
     glass whose principal focal distance is one meter.
     [1913 Webster]