Radiolaria \Ra`di*o*la"ri*a\ (r[=a]`d[i^]*[-o]*l[=a]"r[i^]*[.a]), n. pl. [NL. See {Radioli}.] (Zool.) Order of rhizopods, usually having a siliceous skeleton, or shell, and sometimes radiating spicules. The pseudopodia project from the body like rays. It includes the polycystines. See {Polycystina}. [1913 Webster]