Yes, there is a "Rook" overdrive mode. This mode is attained by successfully blocking an enemies magic attacks by using Nul spells, reflect, or something of that sort. Here's the breakdown of how many times a character must block an enemies magic attack to obtain "Rook":

Tidus- 120
Yuna- 110
Wakka- 120
Lulu- 120
Kimahri- 120
Auron- 120
Rikku- 120

After you get "Rook" your Overdrive gauge will go up 10% every time you block magic.

-DragoonMaster

yes you can get it by blocking magic i think it was 60 times