The Collaborative International Dictionary
turbith
Turpeth \Tur"peth\, n. [NL. turpethum, fr. Per. tirbid a cathartic, turbad a purgative root. Cf. Turbith.] [Written also turbeth, and turbith.]
(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.
(Chem.) A heavy yellow powder, Hg3O2SO4, which consists of a basic mercuric sulphate; -- called also turpeth mineral.
Wiktionary
turbith
n. A type of purgative drug made from the root of a type of morning glory plant, ''Operculina turpethum''; or the plant itself.