| Noun | 1. | gall gnat - fragile mosquito-like flies that produce galls on plantsdipteran, dipteron, dipterous insect, two-winged insects - insects having usually a single pair of functional wings (anterior pair) with the posterior pair reduced to small knobbed structures and mouth parts adapted for sucking or lapping or piercing Cecidomyidae, family Cecidomyidae - gall midges Hessian fly, Mayetiola destructor - small fly whose larvae damage wheat and other grains |