Source : Webster's Revised Unabridged Dictionary (1913)

Uranyl \U"ra*nyl\, n. [Uranium + -yl.] (Chem.)
   The radical {UO2}, conveniently regarded as a residue of many
   uranium compounds.

Source : WordNet®

uranyl
     n : the bivalent radical UO2 which forms salts with acids [syn:
         {uranyl group}, {uranyl radical}]