An ongoing winner in a game or contest.
The defending champion is expected to defeat his challenger.
Someone who is chosen to represent a group of people in a contest.
Barcelona is eligible to play in FIFA Club World Cup as the champion of Europe.
Someone who fights for a cause or status.
champion of women's suffrage
Someone who fights on another's behalf.
champion of the poor
To promote, advocate, or act as a champion for (a cause, etc.).
To challenge.