Irregardless isn’t a word; the word is regardless, which means despite or without regard.
I’m going out regardless of the bad weather means I’m going out despite the bad weather or even though the weather is bad.
The prefix –ir is a negative, so irregardless would mean not despite or not without regard. I’m going out irregardless of the bad weather means I’m going out not despite the bad weather or not even though the weather is bad, which makes no sense.
I’m going to quit my job irregardless of the consequences. This means I’m going to quit without not having any regard for the consequences or not despite the consequences. Again, this makes no sense.
What you want to say is I’m going to quit my job regardless of the consequences, which means I’m going to quit without any regard for the consequences or despite the consequences.
I see that irregardless is in more modern dictionaries as non-standard (it should be in there as substandard), and one on-line dictionary says that it is used in casual speech and writing and sometimes even by more educated people even though it’s considered to be a grammar faux-pas. That is a perfect example of what both Paul and I have said on many occasions: Just because it’s in the dictionary doesn’t mean that it’s correct, and just because someone who is considered to be intelligent uses it doesn’t mean that it’s correct. You have to look beyond that to decipher what’s really going on.
As I like to say, irregardless is not a word regardless of its presence in the dictionary.
Sherry
Sherry’s Grammar List and Paul’s book–Literally, the Best Language Book Ever
Everything Language and Grammar 
Hopefully this doesn’t come off as troll-like — that hopefully is a good indication of my grammatico-political stance — but you raise a point that I’ve long been (genuinely!) curious about:
If having an entry in the dictionary doesn’t mean that something is a word, then how do you make that determination? Do you recognize only the standard words in the dictionary, or do you have some personal rule that tells you when something is a word? I know that statements of the type “X is not a word” are often hyperbolic, but that doesn’t seem to be the case here. I’m perfectly willing to accept that other people have different definitions of the word word, and I’d like to know what your definition is.
Reply from Sherry and Paul: That’s a good question, Dan, and we’re glad you asked. It’s a grey area, but we try to use common sense in addition to basic grammar rules to make those determinations on an individual basis–and we explain it within the blog entry. That way, the reader can understand our logic and then choose for himself whether he wants to use the same logic or follow the dictionary. Generally speaking, though, substandard is incorrect grammar, and non-standard should be a red flag, requiring additional research.
Well in all reality there are several “Bad definitions” in many dictionaries for this “word” [irregardless] Webster’s New International Dictionary (2nd. Ed. Unabridged) described IRREGARDLESS as “an erroneous or humorous form of regardless”
but failed to define what they meant by humorous and many misread that as it’s ok to use the word in a humorous context, when what they meant was it’s humorous to see so many people misuse the word regardless by negating it with the addition of the IR prefix.
Many Dictionaries do not list it at all. Or have it listed in the appendix sections under “easily confused words” or “Commonly Confused Words” with the side note “Use Regardless instead”
However, full vindication came in the form of the Oxford American Dictionary which actually lists the word, (due to the overuse of this incorrect word) But gives the following as it’s definition:
Irregardless: (disp.=REGARDLESS) Though in widespread use, this word should be avoided in favor of Regardless. (See Regardless) Still they need to go one step further to make this word finally disappear and clearly define it as a mistake:
Hence the definition should be worded a little more like:
Irregardless: Irregardless is not an actual word. It is an incorrect usage of the word Regardless. As it’s meaning would clearly be the same as having regard. Though it is a common mistake that is now in widespread use, the word should be avoided in favor of regardless
I believe it has to be clearly defined as many proponents of the “word” “Irregardless” are starting to use the more vague definitions of some of the lesser dictionaries as support for the “so called word”.