/ray'dee oh lair"ee euhn/ , n.
any minute, marine protozoan of the class Radiolaria, or, in some classification schemes, the superclass Actinopoda, having an amebalike body with radiating, filamentous pseudopodia and a usually elaborate outer skeleton.
[ 1875-80; Radiolari ( a ) name of the group (L radiol ( us ) a small beam, equiv. to radi ( us ) RADIUS + -olus -OLE 1 + -aria -ARIA) + -AN ]