What is "artiad"

Artiad \Ar"ti*ad\, a. [Gr. ? even, fr. ? exactly.] (Chem.) Even; not odd; -- said of elementary substances and of radicals the valence of which is divisible by two without a remainder.

a. (context chemistry English) even; not odd; said of elementary substances and radicals whose valence is divisible by two without a remainder.