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. [ 1913 Webster ]

2. (Chem.) (a) Litmus. [ Obs. ] (b) A purple dye obtained from the plant turnsole. See def. 1 (d). [ 1913 Webster ]