Definition from Wiktionary, the free dictionary
Alternative forms 
basionym (plural basionyms)
- (botany, taxonomy) An earlier valid scientific name of a species that has since been renamed and from which the new name is partially derived.
- The name, Arundinaria distans is the basionym of Colanthelia distans.
Usage notes 
The International Code of Botanical Nomenclature includes the following normative definition:
- A previously published legitimate name-bringing or epithet-bringing synonym from which a new name is formed for a taxon of different rank or position (Art. 33.4, 49.1 and 52.3)