Parry bonus
The parry bonus (PB%) is a defensive bonus. It is similar to your dodge bonus (DB%). There are some notable differences though.
While your parry bonus is divided by the number of opponents you are facing in combat, your dodge bonus is not. You will dodge just as well against 3 enemies as you do against one. While you will only block hits (parry) from enemies 33% as well when facing 3 enemies.
Your parry bonus is most affected by the weapon and shield you are using, along with your skill in that particular weapon. High strength and dexterity will help boost your affinity for the parry skill (warrior class), which will in turn boost your parry bonus significantly.
There are also some other rare items that can boost your parry bonus, along with the "bless" spell.
In general, slashing weapons will provide the best parry bonuses, daggers, axes, concussion weapons, and spears will provide moderate bonuses, and two-handed weapons will provide the least parry bonus.