radiolaria UK /ˌɹeɪ.di.ə(ʊ)ˈlɛəɹi.ə/US /ˌɹeɪ.di.oʊˈlɛɹi.ə/ noun[plural only]1 •The 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. — 2012
