Grog's teachings includes deflecting big blows from others' greatswords. And you can keep your balance, but it looks like men swinging their swords against each other and making big clanging noises.
Combat Expertise, Weapon Focus (Greatsword), Student of Grog, Attack Bonus +3
You can give up a bonus of +3 of your attack bonus and add that to your AC Bonus while fighting someone with a Greatsword, in addition to your regular Combat Expertise bonus.
After ten rounds of trying to bash each other, however, you have to rely on your Combat Expertise feat as you tire out quickly.