/terrn"sohl'/ , n.
1. any of several plants regarded as turning with the movement of the sun.
2. heliotrope (def. 2).
3. a European plant, Chrozophora tinctoria, of the spurge family, yielding a purple dye.
4. the purple dye prepared from this plant; litmus.
[ 1325-75; ME turnesole tournesol the dye tornasole the plant, lit., (it) turns (toward the) sun, on the model of Gk heliotrópion HELIOTROPE ]