1. relating to or containing the azo radical
The Collaborative International Dictionary of English v.0.48:
Azo- \Az"o-\ [See Azote.] (Chem.)
A combining form of azote;
(a) Applied loosely to compounds having nitrogen variously
combined, as in cyanides, nitrates, etc.
(b) Now especially applied to compounds containing a two atom
nitrogen group uniting two hydrocarbon radicals, as in
azobenzene, azobenzoic, etc. These compounds furnish many
artificial dyes. See Diazo-.