to lie in wait: to stay hidden in order to spring out and attack or seize
The picture behind this word is always the same: someone is concealed and waiting, poised to strike the moment a target comes within reach. It is the opposite of an open, face-to-face fight. The threat stays hidden until it is too late to escape, which is exactly what makes it so dangerous.
The Bible uses this single idea in three settings that share that core but feel different to a reader. On the battlefield it is the tactic of the ambush, a force tucked out of sight to fall on the enemy from behind, as in the famous trap Joshua set for the city of Ai. In the language of moral warning it describes predators among people, the violent and the greedy who crouch unseen to pounce on the helpless, a favorite image of the Psalms and Proverbs. And it can describe the seducer waiting in the shadows to catch a victim.
In every case the menace lies in the hiding. The word carries the patience of a hunter and the treachery of an attack that gives no warning, whether the one waiting is an army, a robber, or a tempter.