To parry is to use your weapon to block/reflect an incoming attack with said weapon. The reason they have a '0' next to them (I'm guessing) is because that particular type of weapon has no real bonus to parrying...i.e.: it wasn't really designed to be used that way.
I would guess that it was a more recent addition to the stats, and has not actually been filled in with values for each weapon after it was added. I assume it will be before combat actually becomes possible.
"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."