Cac"o*dyl (?), n. [Gr. &?;&?;&?;&?;&?;&?;&?; ill-smelling (kako`s bad + &?;&?;&?;&?;&?; to smell) + -yl.] (Chem.) Alkarsin; a colorless, poisonous, arsenical liquid, As₂(CH₃)₄, spontaneously inflammable and possessing an intensely disagreeable odor. It is the type of a series of compounds analogous to the nitrogen compounds called hydrazines. [Written also cacodyle, and kakodyl.]