The Collaborative International Dictionary of English v.0.48:

Radioli \Ra*di"o*li\ (r[.a]*d[imac]"[-o]*l[imac]), n. pl.; sing.
   Radiolus (r[.a]*d[imac]"[-o]*l[u^]s). [NL., dim. of L.
   radius radius: cf. L. radiolus a feeble sunbeam.] (Zool.)
   The barbs of the radii of a feather; barbules.
   [1913 Webster]