BISTORT

[bis.tort] n [MF bistorte, fr. (assumed) ML bistorta, fr. L bis + torta, fem. of tortus, pp. of torquere to twist--more at torture] (1578): any of several polygonums; esp: a European herb (Polygonum bistorta) or a related American plant (P. bistortoides) with twisted roots used as astringents