nail down ( nailing, nailed, nails )

• 1. 

  PHRASAL VERB If you nail down something unknown or uncertain, you find out exactly what it is. 弄清

  例：

  It would be useful if you could nail down the source of this tension.

  如果你能弄清这种紧张情绪的根源，会是有用的。

• 2. 

  PHRASAL VERB If you nail down an agreement, you manage to reach a firm agreement with a definite result. 确定 (协议)

  例：

  The Secretary of State and his Russian counterpart met to try to nail down the elusive accord.

  美国国务卿与俄罗斯外交部长会晤，试图确定这项表述模糊的协议。