Source : Webster's Revised Unabridged Dictionary (1913)

Heliotrope \He"li*o*trope\, n. [F. h['e]liotrope, L.
   heliotropium, Gr. ?; ? the sun + ? to turn, ? turn. See
   {Heliacal}, {Trope}.]
   1. (Anc. Astron.) An instrument or machine for showing when
      the sun arrived at the tropics and equinoctial line.

   2. (Bot.) A plant of the genus {Heliotropium}; -- called also
      {turnsole} and {girasole}. {H. Peruvianum} is the commonly
      cultivated species with fragrant flowers.

   3. (Geodesy & Signal Service) An instrument for making
      signals to an observer at a distance, by means of the
      sun's rays thrown from a mirror.

   4. (Min.) See {Bloodstone}
      (a) .

   {Heliotrope purple}, a grayish purple color.