n. a foreign substance added to a material to alter its properties; -- a process used. e.g., in making semiconductors from pure silicon in the manufacture of semiconductor chips and integrated circuits. [ PJC ]

n. [ Endo- + parasite. ] (Zoöl.) Any parasite which lives in the internal organs of an animal, as the tapeworms, Trichina, etc.; -- opposed to ectoparasite. See Entozoön. -- En`do*par`a*sit"ic a. [1913 Webster]

a. [ Levo- + DOPA, dihydroxyphenylalanine. ] (Chem. & Biochem.) A substance used as a therapy for Parkinson's Disease; the L form of Dopa; L-dihydroxyphenylalanine; L-hydroxytyrosine (C9H11NO4); also called L-dopa. In the body it is converted by the enzyme dopa-decarboxylase into dopamine, the form in which it is active in the brain, affecting neural impulse transmission. [ PJC ]