/ ˈtʃæmpiən; NAmE / noun , verb
■ noun
1.
a person, team, etc. that has won a competition, especially in a sport :
the world basketball champions
a champion jockey / boxer / swimmer , etc.
the reigning champion (= the person who is champion now)
2.
champion (of sth) a person who fights for, or speaks in support of, a group of people or a belief :
She was a champion of the poor all her life.
■ verb
[ vn ] to fight for or speak in support of a group of people or a belief :
He has always championed the cause of gay rights.
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WORD ORIGIN
Middle English (denoting a fighting man): from Old French , from medieval Latin campio(n-) fighter, from Latin campus level ground, specifically applied to the Campus Martius in Rome, used for games, athletic practice, and military drill..