Toughness measures a creature's ability to resist physical damage and pain, and reflects such factors as the toughness of its flesh, hide or skin. The tougher a creature is the better it can survive enemy blows or shots.
Toughness
Source: Core Rulebook 3E, p. 38
A creature's ability to resist physical damage and pain; the tougher a creature, the better it survives blows or shots.