turn·sole | \ˈtərnˌsōl\
plural -s

Definition of turnsole 

1 : any of several plants whose flowers or stems are supposed to follow the movement of the sun:

a : heliotrope sense 1b

b : sunflower

c : sun spurge

d : a double-flowered tulip (Tulipa suaveolens) of southern Russia

2 : a European annual herb (Chrozophora tinctoria) of the family Euphorbiaceae the juice of which is turned blue by ammonia

3a : a purple dye obtained from the turnsole (see turnsole sense 2)

b : litmus

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History and Etymology for turnsole

Middle English turnesole, from Middle French tournesol, from Old Italian tornasole, from tornare to turn (from Medieval Latin) + sole sun, from Latin sol (accusative solem)

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