Few words draw the ire of grammarians as swiftly as irregardless. The term has been in use in English for over a century, but whether or not it’s a “real word” or one you should use in daily conversation continues to be the subject of debate.
Irregardless is a nonstandard synonym for regardless, which means “without concern as to advice, warning, or hardship,” or “heedless.” Its nonstandard status is due to the double negative construction of the prefix ir- with the suffix -less. The prefix ir- means “not,” while the suffix -less means “without,” literally translating to “not without regard.” This, of course, is the opposite of what English speakers generally intend to convey when using this term; for this reason, style guides unanimously urge against using irregardless.
Although editors purge irregardless from most published writing, the term is alive and well in spoken English and is recorded in most dictionaries. Those who use it may do so to add emphasis.
The bottom line is that irregardless is indeed a word, albeit a clunky one. That said, to avoid the wrath of your grammar-loving friends, it’s safest to avoid using irregardless altogether.