The definition of pesky is someone or something that is annoying and causes trouble.
A little sister that annoys you and follows you everywhere is an example of a pesky little sister.
Informal annoying; disagreeable; troublesome
Origin of peskyprobably variant, variety of pesty ; from pest + -y
adjectivepes·ki·er, pes·ki·est Informal
Troublesome; annoying: a pesky mosquito.
Origin of peskyProbably alteration of pest.
Possibly from pesty.