It means teh b3s7 of t3h 1337!

So totally better than you and then some. The best of everything and everyone. So much better than you, your mom, and your dog. Better than 1337, more than 1337, overly 1337, so 1337 it's painful. The best of all and everything and you and your dog.

Contraction of über (also, though incorrectly, known as uber) and 1337.

A dialect of 1337 language. Uber 1337 differs to 1337 is that it uses as many symbols, ascii and numbers as possible to make a word, uber 1337 contains as few actual letters as possible.

its used as a extention for 1337 it means more 1337 or very 1337 and is offerd used like "I am to 1337 for you" "No way! I am uber 1337!"