Regardless vs. Irregardless

Regardlessadjective

Having no regard; heedless; careless.

Regardlessadverb

Without attention to warnings or indications of bad consequences.

Regardlesspreposition

Paying no attention to; regardless of.

Regardlessadjective

Having no regard; heedless; careless; as, regardless of life, consequences, dignity.

Regardlessadjective

Not regarded; slighted.

Regardlessadjective

(usually followed by `of') without due thought or consideration;

Regardlessadverb

in spite of everything; without regard to drawbacks;

Irregardlessadjective

Irrespective, regardless.

Irregardlessadverb

regardless; a combination of irrespective and regardless sometimes used humorously

Irregardless

Irregardless is a word sometimes used in place of regardless or irrespective, which has caused controversy since the early twentieth century, though the word appeared in print as early as 1795.