Source : Webster's Revised Unabridged Dictionary (1913)

Radiolarian \Ra`di*o*la"ri*an\, a. (Zo["o]l.)
   Of or pertaining to the Radiolaria. -- n. One of the
   Radiolaria.

Source : WordNet®

radiolarian
     n : protozoa with amoeba-like bodies and radiating filamentous
         pseudopods