It’s apparently british slang having something to do with large bouncy appendages of the fairer sex.
Here’s the thread I got it from.
http://www.freerepublic.com/focus/chat/2346547/posts
I see it's mostly in the UK newspapers, and named after "Big Brother 5 (UK)" contestant Shell Jubin, a bodaciously tata-gifted lady. There are many variations based on the jub- or juba- root word, most of them not typeable by my ladylike fingers. :o/
Thanks for the mammaries.