pf2e.fyi
From Pathfinder Advanced Player's Guide, which isn't enabled.

Twinned Defense (Swashbuckler)

FEAT 14
STANCESWASHBUCKLER
Activity 1 action
Prerequisites Twin Parry
Requirements You are wielding two melee weapons, one in each hand

You're always ready to use your off-hand weapon to interfere with attacks against you. While you are in this stance, you constantly gain the benefits of the Twin Parry action.

Pathfinder Advanced Player's GuideOGL