Attack of Opportunity Feat 6
Source Pathfinder Advanced Player's Guide
Trigger A creature within your reach uses a manipulate action or a move action, makes a ranged attack, or leaves a square during a move action it's using.
You swat a foe that leaves an opening. Make a melee Strike against the triggering creature. If your attack is a critical hit and the trigger was a manipulate action, you disrupt that action. This Strike doesn't count toward your multiple attack penalty, and your multiple attack penalty doesn't apply to this Strike.
Traits
Anything that doesn't list another rarity trait (uncommon, rare, or unique) automatically has the common trait. This rarity indicates that an ability, item, or spell is available to all players who meet the prerequisites for it. A creature of this rarity is generally known and can be summoned with the appropriate summon spell.
BarbarianThis indicates abilities from the barbarian class.
ChampionThis indicates abilities from the champion class.
MagusThis indicates abilities from the magus class.
SwashbucklerThis indicates abilities from the Swashbuckler class.