\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) .