from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A persistent irritating critic; a nuisance.
- n. One that acts as a provocative stimulus; a goad.
- n. Any of various flies, especially of the family Tabanidae, that bite or annoy livestock and other animals.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any dipterous insect of the family Oestridae, commonly known as botflies.
- n. A horsefly: any of various species of fly, of the family Tabanidae, noted for buzzing about animals and sucking their blood.
- n. One who upsets the status quo by posing upsetting or novel questions, or attempts to stimulate innovation by proving an irritant.
- n. One who merely irritates without making useful suggestions.
- n. A bloodsucker
from the GNU version of the Collaborative International Dictionary of English
- n. Any dipterous insect of the genus Oestrus, and allied genera of botflies.
from The Century Dictionary and Cyclopedia
- n. The popular name of sundry flies which goad or sting domestic animals, as a breeze, breeze-fly, or horse-fly; specifically, a dipterous insect of the family Tabanidæ and suborder Brachycera, representing also a superfamily Hexachætæ.
- n. A common though erroneous name of sundry flies (bot-flies) of the family Œstridæ and genus Œstrus or Hippoderma, belonging to a different series of the great order Diptera from that of gadflies proper.
- n. Figuratively, one who is constantly going about; a mischievous or annoying gadabout.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a persistently annoying person
- n. any of various large flies that annoy livestock
gad2 + fly2.(American Heritage® Dictionary of the English Language, Fourth Edition)
"fly which bites cattle", from Old Norse gaddr ("spike"). (Wiktionary)