Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
irregardless (adv., adj.)
is a word, all right, a blend probably of irrespective and regardless, but it is a Substandard one, limited to Common and Vulgar English. If a jocular use of it is taken to be an inadvertent one, the user may be judged harshly. Stick with regardless. See PRESCRIPTIVE AND DESCRIPTIVE GRAMMAR AND USAGE.
