/ prəˈtægənɪst; NAmE / noun ( formal )
1.
the main character in a play, film / movie or book
—compare hero
2.
one of the main people in a real event, especially a competition, battle or struggle
3.
an active supporter of a policy or movement, especially one that is trying to change sth
SYN champion :
a leading protagonist of the conservation movement
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WORD ORIGIN
late 17th cent.: from Greek prōtagōnistēs , from prōtos first in importance + agōnistēs actor.