You can use your combat skill for defense as well as offense.
Benefit:When you use the attack or full attack action in melee, you can take a penalty of as much as –5 on your attack roll and the same number (+5 or less) as a dodge bonus to your AC. This number may not exceed your base attack bonus. The changes to attack rolls and AC last until your next action.
Normal:Characters without Combat Expertise can fight defensively while using the attack or full attack action to take a –4 penalty on attack rolls and gain a +2 dodge bonus to AC.
Special:Warriors can select Combat Expertise as one of their warrior bonus feats.