User blog comment:B214/Question and Answers 6/@comment-185.112.105.215-20170106035554/@comment-29963364-20170106221150

Omega, here are some of your quotes...

["So, its not really irregular in the traditional sense. However, its neither regular either. it's its own thing."

"Issei has a regular balance breaker, Scale Mail, the Illigal Move Trinia is something else entirely."]

You just said exactly what an Irregular is. And I've been saying this the whole time. An Irregular BB is something that can't be categorized as the others:

* Regular

* Sub-Species

* Abyss-Side

So Azazel, the leading specialist on Sacred Gears, created a whole different category to refer to the "non-regular" BB's.

Yes, Issei has access to his Regular BB, unlike Yuuto and Saji. But Issei took it and used his modified Evil Pieces to created something that can't be called a Regular, a Sub-Species, or an Abyss-Side.

So, since it is something that is non of the above mentioned categories, it is called an Irregular Balance Breaker.