Main Entry: ra·di·o·lar·i·an

Pronunciation: \ˌrā-dē-ō-ˈler-ē-ən\

Function: noun

Date: 1875

: any of three classes (Acantharia, Polycystina, and Phaeodaria) of usually spherical chiefly planktonic marine protozoans having radiating threadlike pseudopodia and often a siliceous skeleton of spicules

— radiolarian adjective

[radiolarian illustration]