Defensive Sweep( Player's Handbook II, p. 78)
[Fighter Bonus Feat, General]
You sweep your weapon through the area you threaten, warding away opponents and forcing them to move away or suffer a fearsome blow.
Base attack bonus +15,
If an opponent begins his action adjacent to you and does not move, he provokes an attack of opportunity from you immediately after his turn ends, provided that you threaten the square that he occupies. Any sort of movement, including a 5-foot step, allows the opponent to avoid provoking this special attack of opportunity. This feat does not give you any ability to make additional attacks of opportunity in a given round.
A fighter can select Defensive Sweep as one of his fighter bonus feats.