Turpeth \Tur"peth\, n. [NL. turpethum, fr. Per. tirbid a cathartic, turbad a purgative root. Cf. {Turbith}.] [Written also {turbeth}, and {turbith}.] 1. (Bot.) The root of {Ipom[oe]a Turpethum}, a plant of Ceylon, Malabar, and Australia, formerly used in medicine as a purgative; -- sometimes called {vegetable turpeth}. 2. (Chem.) A heavy yellow powder, {Hg3O2SO4}, which consists of a basic mercuric sulphate; -- called also {turpeth mineral}.