pyrrole /ˈpɪɹəʊl/ noun1 •Any of a class of aromatic heterocyclic compounds containing a ring of four carbon atoms and a nitrogen atom; especially the simplest one, C₄H₅N.The way the red crystals absorbed light suggested that the molecule might contain a porphyrin-like structure, a flat ring made up of four smaller rings called pyrroles […]. — 1998 formspyrroles
