"Zenryoku-tōkyū全力投球" literally means "full-power pitching" but describes giving your absolute all to any task.
It's about putting 100% effort and energy into something, holding nothing back.
EX.
「今回(こんかい)の期末試験(きまつしけん)は全力(ぜんりょく)でがんばります!」
"I'll do my best on this final exam!"