Reactions
Reactions are special actions that can be taken out of turn order in response to certain triggers, such as enemy attacks or movement. Unless specified otherwise, once you take a Reaction you cannot take it again until the beginning of your next turn. Even if a Reaction is usable 2/round or more, your uses of it only refresh when your next turn begins.
You can only take one Reaction per turn – your turn or other characters’ turns – but you can take any number of Reactions per round, as long as you have reactions still available.
By default, all mechs can take the Brace and Overwatch reactions. Certain systems and talents can grant other Reactions.