siskin /ˈsɪskɪn/ noun2 •A small green and yellow European finch, Carduelis spinus spinus or Carduelis spinus, now Spinus spinus.I sat there on a bench in dappled shade, beside an aviary full of brightly feathered finches and siskins fluttering about. — 2001 •Any of various similar birds in subfamily Carduelinae, principally in the genus Spinus. formssiskins