thiazine

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of a class of organic chemical compounds containing an aromatic ring containing one sulfur atom, one nitrogen atom, and four carbon atoms. Thiazines are often used in making dyes, drugs, and insecticides.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun organic chemistry A six-membered heterocycle containing four carbon atoms, one nitrogen and one sulfur atom, and two double bonds; many of its derivatives have important applications

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a compound made up of a ring of four carbon atoms and one sulfur atom and one nitrogen atom