-rbə̇n noun
( -s )
Etymology: International Scientific Vocabulary phorb- (Greek phorbē pasture, fodder) + -in — more at pheophorbide
1. : a magnesium-free compound C 22 H 18 N 4 that is the parent of chlorophyll in that it contains the unsubstituted ring structure of chlorophyll consisting of one carbocyclic ring in addition to the porphin ring system
2. : any of several magnesium-free derivatives of chlorophyll (as pheophytin) that contain its characteristic ring structure — compare chlorin