Source : Webster's Revised Unabridged Dictionary (1913)

Turnsole \Turn"sole`\, n. [F. tournesol, It. tornasole; tornare
   to turn (LL. tornare) + sole the sun, L. sol. See {Turn},
   {Solar}, a., and cf. {Heliotrope}.] [Written also {turnsol}.]
   1. (Bot.)
      (a) A plant of the genus {Heliotropium}; heliotrope; -- so
          named because its flowers are supposed to turn toward
          the sun.
      (b) The sunflower.
      (c) A kind of spurge ({Euphorbia Helioscopia}).
      (d) The euphorbiaceous plant {Chrozophora tinctoria}.

   2. (Chem.)
      (a) Litmus. [Obs.]
      (b) A purple dye obtained from the plant turnsole. See
          def. 1
      (d) .