Source : Webster's Revised Unabridged Dictionary (1913)

Hyporadius \Hy`po*ra"di*us\, n.; pl. {Hyporadii}. [Pref. hypo- +
   radius.] (Zo["o]l.)
   One of the barbs of the hypoptilum, or aftershaft of a
   feather. See {Feather}.