An annoying person can be described as a PEST, NUISANCE, BLIGHTER, PRIG, BORE, PAIN, TWIT, irker, or GADFLY. A PEST is someone who is constantly causing trouble and disruption. A NUISANCE is someone who is bothersome and irritating. A BLIGHTER is an informal term for someone who is unpleasant or annoying. A PRIG is someone who is overly moralistic and judgmental. A BORE is someone who is dull and tedious. A PAIN is someone who is difficult to deal with. A TWIT is someone who is foolish or silly. An irker is someone who is irritating and exasperating. Finally, a GADFLY is someone who is persistently annoying.