未だ未だ (madamada) adv. - still some way to go before goal; still more to come; much more; not yet
An amusing alliteration, if nothing else. Of course, it's pretty easy to do such a thing, due to the structure of the "letters"... Still, it's certainly useful in many cases. The one that's likely to be taught first in a real Japanese class would be using "madamada" as part of a response to a compliment of your skills in some area. In an anime setting, it's more likely to be heard either from someone in a losing position who isn't giving up, or from someone refusing to let up.