The period of time from the end of one quidditch season to the start of the next one. As its the only sport in harry potter, sports fans at hogwarts are left with nothing to watch during these six or so months.
similar to the few months after the nfl season ends until the mlb season starts.
Ron: turn off espn. all they're showing is highlights from last month's quidditch championship
harry: maybe if JK Rowling had invented more than one sport we wouldn't be stuck in quidditch offseason.