Overwatch

Overwatch is an ability unlocked at Ranged Combat or Close Combat level 4. It is also available at Throwing Weapons level 4 starting from the Director's Cut of Shadowrun: Dragonfall. Overwatch is unique in that it allows the selected character to react and respond automatically to enemy movement and abilities during their opponents turn.

Overview
When used, Overwatch allows your characters to monitor a certain area. If an enemy walks into or performs an action in that space, you will automatically fire. It's useful for holding a doorway and getting a vicious first strike on your enemies. It also allows you to prepare defensively for enemies you are expecting but can not currently see or engage with.

You can activate overwatch by pushing the button to the right of your "action selector". It looks like a ball with a semi-circle above it. Make sure to set your facing correctly as only targets within that cone will trigger an Overwatch attack.

Note that overwatch is activated with your currently selected ability. This means you should generally overwatch with your strongest remaining ability (e.g. burst fire, aimed short). You can also overwatch with melee weapons.

Using overwatch will end that characters turn for the round, so make sure you complete all other required actions (e.g. movement or reloading) before selecting overwatch.