Home › Words › N › norleucinenorleucinenorleucine means an isomer of leucine, not found in natural proteins, used in experimental studies of protein structure and function.EtymologyFrom nor- + leucine.nounAn isomer of leucine, not found in natural proteins, used in experimental studies of protein structure and function.Definitions & examples from Wiktionary (CC BY-SA 3.0).