Source : Webster's Revised Unabridged Dictionary (1913)

Goniometer \Go`ni*om"e*ter\, n. [Gr. ? angle + -meter: cf. F.
   goniom[`e]tre.]
   An instrument for measuring angles, especially the angles of
   crystals, or the inclination of planes.

   {Contact, or Hand}, {goniometer}, a goniometer having two
      movable arms (ab, cd), between which (at ab) the faces of
      the crystals are placed. These arms turn about a fixed
      point, which is the center of the graduated circle or
      semicircle upon which the angle is read off.

   {Reflecting goniometer}, an instrument for measuring the
      angles of crystals by determining through what angular
      space the crystal must be turned so that two rays
      reflected from two surfaces successively shall have the
      same direction; -- called also {Wollaston's goniometer},
      from the inventor.

Source : WordNet®

goniometer
     n : direction finder that determines the angular direction of
         incoming radio signals