gadfly

Noun

A fly that bites livestock; an annoying, stimulating person.
a persistently annoying person
any of various large flies that annoy livestock
Any dipterous (“two-winged”) insect or fly of the family Oestridae (commonly known as a botfly) or Tabanidae (horsefly), noted for irritating animals by buzzing about them, and biting them to suck their blood; a gadbee.
A person or thing that irritates or instigates.
A person or thing that irritates or instigates.
A person who upsets the status quo by posing novel or upsetting questions, or attempts to stimulate innovation by being an irritant.
Synonym of gadabout (“a person who restlessly moves from place to place, seeking amusement or the companionship of others”).
A person who takes without giving back; a bloodsucker.

Examples

He’s a regular gadfly and takes advantage of his friend’s generosity.
His opponent was a gadfly, constantly challenging his plays and questioning definitions.

Origin / Etymology

From gad (“(obsolete) sharp point, spike; (dialectal) sharp-pointed rod for driving cattle, horses, etc., goad”) + fly, in the sense of a fly which irritates cattle, etc., by biting them, similar to the prodding of a goad. Gad is derived from Middle English gad, gadde (“metal spike with a sharp point; stick with a sharp point for driving animals, goad; metal bar or rod, ingot; (by extension) lump of material; metal rod for measuring land; (by extension) unit of linear measure equal to about 10 to 16 feet”), borrowed from Old Norse gaddr (“spike; goad”), from Proto-Germanic *gazdaz (“spike; goad”), further etymology uncertain.
Sense 2.1.1 (“person who upsets the status quo”) may allude to the Apology by the Greek philosopher Plato (428/427 or 424/423 – 348/347 B.C.E.), where he describes Socrates (c. 470 – 399 B.C.E.) acting as a goad to the Athenian political scene like a gadfly (Ancient Greek μῠ́ωψ (mŭ́ōps)) arousing a sluggish horse.

Synonyms

blighter, cuss, pest, pesterer, bloodsucker, bummer, eccentric, free rider, free spirit, freeloader, gadabout, gadfly, heteroclite, individualist, leech, maverick, misfit, mooch, moocher, nonconformist, offbeat, parasite, scrounge, scrounger, scunge, smell-feast, social butterfly, sponge, sponger, stoat-fly, stout, sucker, trencher mate, warble fly

Scrabble Score: 14

gadfly: valid Scrabble (US) TWL Word
gadfly: valid Scrabble Word in Merriam-Webster MW Dictionary
gadfly: valid Scrabble Word in International Collins CSW Dictionary

Words With Friends Score: 15

gadfly: valid Words With Friends Word