n.
  - a person who has surpassed all rivals in a sporting contest or other competition.
- a defender of a cause or person. ▸historical a knight who fought in single combat on behalf of the monarch. 
v.
 support the cause of.
adj.
 Brit. informal or 
dialect excellent.
Etymology
  ME: from OFr., from med. L. campio(n-) ‘fighter’, from L. campus (see camp1).