pyrrole

Etymology

From German Pyrrol, corresponding to Ancient Greek πυρρός (purrhós, “reddish, fiery”) + -ole.

noun

1. (organic chemistry) 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, Georgina Ferry, Dorothy Hodgkin: A Life