punch above one's weight字面含义为打败重量更大的选手，引申义为超常发挥取胜，以小博大。

【例句】
This player seems to be able to constantly punch above his weight.
这名选手似乎总能击败实力比他强的对手。

He defeated his opponent with punch above his weight.
他以小博大击败了对手。