veriest muchly irregardless anyways ain't
Answer:
All five.
The Third International, first published in 1961, was famous for aiming to describe language as it is really used, not as experts decreed it should be used. It broke with previous dictionaries by acknowledging the existence of words you wouldn't use in a formal setting: slang, dialect, obscenities, and so on.
This, of course, sparked outrage. Essays appeared denouncing the new dictionary as proof of the decline of civilization, and opponents of the Third even created a rival dictionary to restore propriety.
In Dr. Shapiro's view, the controversy was rather overblown. If you looked up a word like "irregardless" in the Third, you found not only a definition, but a usage note explaining that the word in question was regional, or colloquial, or even substandard (ouch!). A person who looked up "irregardless" in the Third got useful information and advice; a person who looked it up in other dictionaries got nothing but doubt about whether they had spelled it properly. But perhaps Dr. Shapiro cannot be trusted to be impartial about this. His grandfather, Warren B. Austin, was an assistant editor for the Third.
Cheers to the many of you who sent in your guesses, but only one of you was bold enough to guess that all five words were in the dictionary: Leo S.! And thanks to Agniv for this: "Irregardless of the words, some people just ain't going to use them."