Its etymology derives from the Latin word for of authors, and is abbreviated auct.
It is often used in conjunction with nec or non to indicate a misapplied name, e.g. "Leucospermum bolusii auct.
It may be qualified to indicate the number of authors, e.g. auctorum multorum (abbreviated auct.
[1] If the name Leucospermum bolusii is used in a later publication, the botanical author needs to make clear which one is meant, and which one isn’t.
The Flora Europaea gives one of the synonyms of Cistus clusii as "C. libanotis auct.