No word receives as much lexical scorn as "irregardless" - I felt a shiver just typing it. But unlike the made-up terms it often gets lumped in with, including "supposably" and "sherbert", irregardless is technically a real word. The Merriam-Webster dictionary says so.
Kory Stamper, a lexicographer for Merriam-Webster and author of Word by Word: The Secret Life of Dictionaries, explains in this video that the word was first used in dialectical American speech in the early 20th century and remains somewhat common in spoken English.
It means "regardless" and is a blend of two words: "irrespective" and "regardless".
In the dialect that it comes from, "irregardless" is an emphatic "regardless". So if you're a native speaker of particular dialects that use the word, Stamper tells Business Insider that you might have a conversation like this:
I might say, "Dad, let me borrow the car. I'm a really good driver." And he'll say, "Regardless, I'm not comfortable." I'll say, "Oh but come on. I'll get it detailed, and I'll put gas in it." He'll say, "Irregardless, no." The point of the "irregardless" is to shut down conversation.
In standard English, though ... no. It's clunky and it's easy to assume that the prefix "ir" would make it "not regardless", which ... huh? Stamper notes that "just because a word's a word doesn't necessarily mean you should use it" and encourages people to use "regardless" instead.
Repeating for emphasis: Use "regardless" instead.
If reading this post is giving you an angry tic, rest assured that the word is probably not making a comeback. According to a Grammarly poll, 74 per cent of voters say "irregardless" is not a real word, though we all know how much weight the popular vote has.