Uncanny Dodge

This class feature is gained by Barbarians at 2nd level and by Rogues at 4th level. A character with Uncanny Dodge retains his Dexterity modifier to AC (if any) even if he is caught flat-footed or struck by an invisible attacker. However, he still loses his Dexterity modifier to AC if immobilized.

If a Barbarian or Rogue already has uncanny dodge from a different class, he automatically gains Improved Uncanny Dodge instead.