Noun. 1. Parazoa-multicellular organisms having less-specialized cells than in the Metazoa; comprises the single phylum Porifera. subkingdom Parazoa. animal kingdom, Animalia, kingdom Animalia-taxonomic kingdom comprising all living or extinct animals.phylum Porifera, Porifera-coextensive with the subkingdom Parazoa: sponges.oun. 1. Parazoa-multicellular organisms having less-specialized cells than in the Metazoa; comprises the single phylum Porifera. subkingdom Parazoa. animal kingdom, Animalia, kingdom Animalia-taxonomic kingdom comprising all living or extinct animals.