lie in wait

Remain hidden while preparing to attack, as in The opposition was quietly lying in wait for the incumbent to make his first big mistake. This expression originally alluded to physical attacks and is now often used figuratively. [Mid-1400s] Also see lay for.

The verb has one meaning:

Meaning #1: wait in hiding to attack
  Synonyms: ambush, scupper, bushwhack, waylay, lurk, ambuscade