Source : Webster's Revised Unabridged Dictionary (1913)

Pterygium \Pte*ryg"i*um\, n.; pl. E. {Pterygiums}, L.
   {Pterygia}. [NL., fr. Gr. ?, properly a dim, akin to ? a
   feather.] (Med.)
   A superficial growth of vascular tissue radiating in a
   fanlike manner from the cornea over the surface of the eye.