noun
putting one's heart and soul into each pitch
Baseball term; a yojijukugo expressing the idea of giving everything to every single pitch. Used as a motto or description of a pitcher's attitude.
彼の投球はまさに一球入魂だ。
His pitching is truly putting his heart and soul into every pitch.
一球入魂の精神でマウンドに立つ。
I take the mound with the spirit of putting everything into each pitch.
全力投球 means 'pitching with all one's might' and is more common in everyday speech. 一球入魂 is a more dramatic, set phrase emphasizing spiritual commitment to each individual pitch.
A yojijukugo combining 一球 (one pitch) and 入魂 (putting one's soul into). The exact origin is uncertain, but it is strongly associated with baseball culture in Japan.