The children finally uncorked their energy, running and playing wildly on the playground.

uncorked 是动词 uncork 的过去式。uncork 由前缀 un-（表示"去除"）和名词 cork（软木塞）组成，字面意思是"拔掉瓶塞"。这里用作比喻，表示"释放、发泄"能量或情绪，就像拔掉瓶塞让液体喷涌而出一样。