Combat Stability( Player's Handbook II, p. 87)
[Combat Form, Fighter Bonus Feat]
When you maintain your combat focus, you become diffi cult to dislodge. Your muscles lock into an unyielding position, granting you superior ability to resist trip attacks, bull rushes, disarms, and similar effects.
Combat Focus (PH2) , WIS 13, base attack bonus +3,
You gain a +4 bonus on checks or rolls to resist bull rush, disarm, grapple, overrun, and trip attempts made against you. If you have three or more combat form feats, the bonus granted by this feat increases to +8.
A fighter can select Combat Stability as one of his fighter bonus feats.