gallfly definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
noun pl. gallflies
an insect whose eggs or larvae cause galls when deposited in plant stems, or one which lays its eggs in galls produced by other insects
gallfly definition by American Heritage Dictionary
Any of various small insects, such as the gall midge or gall wasp, that deposit their eggs on plant stems or in the bark of trees, causing the formation of galls in which their larvae grow.