Meh !

I've been seeing the word "Meh" being used on the web --in emails and online communities lately. While the context of the word made it obvious that it was a form of a non-commital indifferent response, I wanted to figure out what its actual meaning was.
So I went a-exploring and found this definition on the urban-dictionary www.urbandictionary.com

Meh:

Meh is used to describe any and every word possible, including:
Yes
No
maybe
kind of
never
always
ok
alright
no thankyou
yes please
look b**** i really dont care so just shut the f*** up
if you want
whatever
If you wnat
i dont want to really
well
shut up
i dont really care
no honestly, i dont care...

...and is never explained on which is actually used...

"you wanna come round mine?"
"meh"
"whats that mean"
(told all of the definitions above)
"so which one? yes or no?"
"meh"
"that a yes?"
"meh"
"a no??"
"meh"
"a maybe???"
"meh?"
"maybe???"
"meh"
"look please tell me"
"meh"......