|part of speech:
||any of various flies, such as the horsefly or botfly, that bite and pester livestock.
The horse swished its tail to shoo the gadflies.
||a persistent critic, esp. of established institutions and policies.
He has become a gadfly of the genetically modified food industry, making regular appearances on television to warn of the health and environmental risks.
||an annoying, insistent pest.
||bother, nuisance, pest, trial, troublemaker