Leaving or Escaping

said to mean that a person that one looks for has fled or left

The key suspect in the investigation vanished without a trace; so it's safe to say that the bird has flown.

(of a soldier) having left one's military duty without being permitted to do so

The soldier is knowingly AWOL, disregarding the consequences of leaving without permission.

to experience a sudden and significant decline, deterioration, or devaluation, often unexpectedly or rapidly

The company's financial situation was stable, but when a major client cancelled their contract, things went south quickly.

moving from one place to another in an attempt to not get caught or arrested

The fugitive has been on the run for weeks, constantly changing locations to evade capture.

to suddenly disappear from sight, particularly in order to hide from someone

He often goes to ground whenever he wants to avoid unwanted attention.

to escape in order to not get caught or not to be with someone

He often gives his younger sister the slip when she tries to tag him during their game.

to leave somewhere, often hastily

He often busts a move when he realizes he's running late for work.

to take action in order to achieve something

No one made a move to help.

running away in an attempt not to get caught

The fugitive is in the wind, having eluded capture once again.

used to refer to a someone or something that suddenly disappears, particularly in a way that is mysterious or suspicious

The magician waves his hand, and the coin disappears into thin air.

an instance of someone becoming impossible to find, particularly when they are needed, wanted, or in a difficult or unpleasant situation

She often pulls a disappearing act at parties, leaving without saying goodbye.

to leave a place secretly and as fast as one can, particularly in order to avoid paying one's debts

He's planning a moonlight flit from his apartment tonight to avoid paying the rent.

to manage to escape from a prison

The inmate is currently attempting to go over the wall as a desperate bid for freedom.