Usage Note: Irregardless is a word that many mistakenly believe to be correct 
usage in formal style, when in fact it is used chiefly in nonstandard speech 
or casual writing. Coined in the United States in the early 20th century, it 
has met with a blizzard of condemnation for being an improper yoking of 
irrespective and regardless and for the logical absurdity of combining the 
negative 
ir- prefix and -less suffix in a single term. Although one might reasonably 
argue that it is no different from words with redundant affixes like debone and 
unravel, it has been considered a blunder for decades and will probably 
continue to be so.
    
Source: The American Heritage® Dictionary of the English Language, Fourth 
Edition
Copyright © 2000 by Houghton Mifflin Company.
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