tetrazole

from The Century Dictionary.

• noun A colorless compound, prepared from aminophenyltetrazole-carboxylic acid. It has acidic properties, crystallizes in lustrous prisms or plates, melts at 155° C., and may be sublimed.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Org. Chem.) A crystalline acid substance, CH2N4, which may be regarded as pyrrol in which nitrogen atoms replace three CH groups; also, any of various derivatives of the same.

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

• noun organic chemistry A five-membered heterocycle having one carbon atom, four nitrogen atoms and two double bonds