“九牛二虎之力”，字面意思是九头牛与两只虎的力气的相加（strength of nine bulls and two tigers），比喻其力大不可挡。常用于形容很费力才做成一件事。可以翻译为“ tremendous effort；all one's strength”。

例句：

我使出九牛二虎之力也没把它拽动。

I heaved with all my might but still couldn't budge it.

他费尽九牛二虎之力把那棵树重新立了起来，并一直照顾它，直到它完全复原。He used all his strength to raise the tree back up again, and looked after it until it completely recovered.