To be enthusiastic or energetic; to be eager and spirited about doing something (sometimes to the point of overexertion).
新しい仕事で彼は張り切っている。
He's very enthusiastic about his new job.
張り切り過ぎて最初の週で疲れてしまった。
He got too eager and was exhausted in the first week.
学園祭の準備でみんな張り切っている。
Everyone is fired up preparing for the school festival.