Needs review
Source: Player's Handbook

Description: Take a penalty to hit your foe to raise your own AC

Prerequisites: INT 13

Required for: Blackened Sight, Breaking Waves, Defensive Strike, Grappling Block, Improved Combat Expertise, Improved Disarm, Improved Feint, Improved Trip, Karmic Strike, One-Strike Blade, Sand Snare, Spellcasting Harrier, Strike at the Tail, The Pincers Hold, The Tail Strikes, Thundering the Sky, Victory of the Wind, Whirlwind Attack

When you use the attack action or the full attack action in melee, you can take a penalty of as much as -5 on your attack roll and add the same number (+5 or less) as a dodge bonus to your Armor Class. This number may not exceed your base attack bonus. The changes to attack rolls and Armor Class last until your next action.

Special: A fighter may select Combat Expertise as one of his fighter bonus feats (see page 38).

Normal: A character without the Combat Expertise feat 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 Armor Class.