TRAIT - Unarmed
An unarmed attack uses your body rather than a manufactured weapon. An unarmed attack isn't a weapon, though it's categorized with weapons for weapon groups, and it might have weapon traits. Since it's part of your body, an unarmed attack can't be Disarmed. It also doesn't take up a hand, though a fist or other grasping appendage follows the same rules as a free-hand weapon.
Source: Core Rulebook pg. 283