Lately I've been noticing more and more people using the word "irregardless," and every time I hear it, I want to raise my hand and be like, "Oooh, Oooh, Mr. Kotter, that's not a word!!!"
(Except I don't because I know how totally obnoxious that would be.)
In any case, when people use the word "irregardless" they usually mean "regardless." Adding the extra negative modifier doesn't change the word.
Then again, the people I hear using it are generally very intelligent people. So you'd think people like that wouldn't use a word that was so blatantly wrong. So maybe "irregardless" has been used incorrectly so many times that it's now correct. Just like "flammable" and "inflammable" now mean the same thing and are both correct.
I checked Wikipedia, the source of all knowledge, and they seem to say that it's controversial whether "irregardless" is a word. Irregardless, it seems that people use it a lot.