An episode is an action or activity that is contained within a brief period of time. The most common use of this word in modern vernacular is to refer to a TV episode which is one showing of a program in a series. In other uses, an episode can be a short period of bad behavior from a child or adult, a brief period of "acting out." In bipolar disorder (hyperlink?) when someone is in a manic phase it is often referred to as a manic episode.