What is "carbazole"

n. 1 (context organic compound English) A tricyclic aromatic organic compound containing two benzene rings fused to a pyrrole ring. 2 (context organic chemistry English) Any of its derivatives.

Carbazole is an aromatic heterocyclic organic compound. It has a tricyclic structure, consisting of two six-membered benzene rings fused on either side of a five-membered nitrogen-containing ring. The compound's structure is based on the indole structure but in which a second benzene ring is fused onto the five-membered ring at the 2–3 position of indole (equivalent to the 9a–4a double bond in carbazole respectively).