to make someone give you exact details or a firm decision about something

They nailed him down to a specific time and place. 他们迫使他确定了时间和地点。

If you nail down an arrangement or decision, you decide and agree to the details of it.

After a five-hour meeting, we finally nailed down a deal. 开了5个小时的会后，我们最终达成了一项协议。

to understand something completely, or to describe something correctly

We haven't been able to nail down the cause of the fire yet. 我们仍未弄清火灾的起因。