Source : Webster's Revised Unabridged Dictionary (1913)

Gallfly \Gall"fly`\, n.; pl. {Gallflies}. (Zo["o]l.)
   An insect that deposits its eggs in plants, and occasions
   galls, esp. any small hymenopteran of the genus {Cynips} and
   allied genera. See Illust. of {Gall}.