Dioptra

1 definition found

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

  Diopter \Di*op"ter\, Dioptra \Di*op"tra\, n. [L. dioptra, fr.
     Gr. ?. See 2d {Dioptric}.]
     An optical instrument, invented by Hipparchus, for taking
     altitudes, leveling, etc.
     [1913 Webster]