radiolaria/ˌɹeɪ.di.ə(ʊ)ˈlɛəɹi.ə/EtymologyFrom subclass name Radiolaria.nounThe members of the taxonomic subclass Radiolaria; radiolarians.“Radiolaria, which are single-celled plankton, are abundant in all regions of the world ocean and older than multicellular life.”