wing nut

wing nut
    n 1: any tree of the genus Pterocarya; fruit is a small winged
         nutlet; Caucasus to southeastern Asia [syn: {wing nut},
         {wing-nut}]
    2: a threaded nut with winglike projections for thumb and
       forefinger leverage in turning [syn: {wing nut}, {wing-nut},
       {wing screw}, {butterfly nut}, {thumbnut}]