Came here to say “Say ‘irregardless’ one more time. I dare you. I double dare you, motherf**ker”, but you pre-empted me — good man!

On the other hand, you’re talking about Merriam-Webster, which is a US dictionary and, therefore, not of any significance nor to be relied upon — remember … if it’s not British, it’s wrong (and that goes doubly so for anything from the US).

However, despite the fact that it’s Merriam-Webster, the thing about the words you find in the dictionary is that the criterion for admission is that there must be evidence of at least one person having previously made use of them … and that’s all — dictionaries have very low standards … I wouldn’t trust them uncritically myself.