From Compendium of Worldly Lore
Needs review
Source: Player's Handbook
Description: You are skilled at dodging past opponents and avoiding blows.
Required for: Blackened Sight, Bounding Assault, Combat Archery, Mobile Defense, One-Strike Blade, Rapid Blitz, Roof-Jumper, Roofwalker, Shot on the Run, Spring Attack, Thundering the Sky, Whirlwind Attack
You get a +4 dodge bonus to Armor Class against attacks of opportunity caused when you move out of or within a threatened area. A condition that makes you lose your Dexterity bonus to Armor Class (if any) also makes you lose dodge bonuses. Dodge bonuses (such as this one and a dwarf's racial bonus on dodge attempts against giants) stack with each other, unlike most types of bonuses.
Special
A fighter may select Mobility as one of his fighter bonus feats.