DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   gallfly
       n 1: small solitary wasp that produces galls on oaks and other
            plants [syn: gall wasp, gallfly, cynipid wasp,
            cynipid gall wasp]
       2: fragile mosquito-like flies that produce galls on plants
          [syn: gall midge, gallfly, gall gnat]
       3: any of various insects that deposit their eggs in plants
          causing galls in which the larvae feed