Louisville Slugger

I heard of a dirty but effective boxing technique called the "louisville slugger."  I doubt you could sneak a baseball bat into a ring.  Can anybody explain what this is?  Are there pix or video?   Is it legal in MMA?

The google says

Louisville Slugger Men's TPX Boxer Shorts with XPS Flex Cup

http://www.baseballexpress.com/catalog/product.jsp?productId=86239

 

Best i can find