being very active; being very useful; playing a very active part; making a spectacular showing; great efforts; splendid work
彼女は今大会で大活躍を見せた。
She put on a spectacular showing in this tournament.
新人選手の大活躍でチームが優勝した。
The team won thanks to the standout play of a rookie.
海外進出した若手選手が国際大会で大活躍したと報じられた。
It was reported that a young player who went abroad put on a great performance at an international competition.