Home › Words › E › extensionistextensionistextensionist · noun — one who favours or promotes extension, such as agricultural extension or moral extensionism.Definition from Wiktionary (CC BY-SA 3.0).EtymologyFrom extension + -ist.nounOne who favours or promotes extension, such as agricultural extension or moral extensionism.Definitions & examples from Wiktionary (CC BY-SA 3.0).