Unrelenting Annoyance is a term that describes a person or thing that is constantly irritating or bothersome. The crossword solution for this term is PEST, which is a four-letter word that is used to describe someone or something that is annoying and difficult to get rid of. This term can be used to describe a person who is always causing trouble or an animal that is constantly invading a space. In either case, the annoyance is relentless and difficult to stop.