primulaceous Syllabification: (prim·u·la·ceous)Pronunciation: /ˌprimyəˈlāSHəs/Definition of primulaceous adjective Botany of, relating to, or denoting plants of the primrose family (Primulaceae). Origin: mid 19th century: from modern Latin Primulaceae (plural), based on medieval Latin primula (see primula), + -ousprimulaceous in other Oxford dictionaries Definition of primulaceous in the British & World English dictionary