If you put the knife into the knife drawer, and all the other knives start shying away from it and pointing, with only a few of the more bold knives sliding slowly over to the new knife, it may well be an irregular knife. Soon, you may start hearing some unusual knife stories and some little paring knives might start showing up.....
Honestly, Julio, I've never even heard of an "irregular" knife. I guess there are seconds in everything! Please pardon my humor. I had nothing I could tell you, so I posted the thoughts in my head at the moment.
I look forward to the other answers you get that will teach us both!