Amalgamation of the words "is" and "it", used either to(worryingly)signify an exclamation or to a question in itself.
Highly meaningless expression
favoured by both chavs
and certain asian/black cultures often found within a similarly indecipherable banter.
Shreena - "Oh ma gosh! He was like, all ova her and like, she was like, geet off me! Like.."
- "Awwww, issit?"
Shreena - "Yea, and I'm like, daz sum ova sheet..."