Abscess: A local accumulation of pus anywhere in the body. The following are some examples of abscesses:

A skin abscess is better known as a common boil; A peritonsillar abscess is a persistent collection of pus behind the tonsils; and A perianal abscess is a pool of pus that forms next to the anus, often causing considerable tenderness and swelling in that area and pain on sitting down and on defecating.