Stun setting

From Memory Alpha, the free Star Trek reference.

The stun setting is term used to describe non-lethal settings of a phaser, phase weapon, or any incapacitating weapon.

There are several degrees of stun settings available on Federation phasers. Effects can range from slight disorientation to unconsciousness and serious injury.

Along with hand weapons, shipboard phaser banks could be modified to deliver a potent stunning beam. This could be useful in incapacitating large crowds from orbit, but was seldom used. (TOS: "A Piece of the Action")

A weapon fired on stun will not usually set off internal alarms on Federation starships, as lethal power settings will. However, a stun setting applied at close range to the brain can kill a target. Muliple stun attacks in short-periods of time can begin to damage a target's central nervous system. (Star Trek VI: The Undiscovered Country; TNG: "Samaritan Snare")