All of the following are examples of nonwords EXCEPT _____.

The term "nonword" typically refers to a term that is not recognized as a legitimate word in standard English. Among the options provided, "can't" is an example of a legitimate contraction of "cannot," which is widely accepted in both spoken and written English. This makes "can't" a recognized word in the language.

In contrast, the other options present nonwords or controversial terms that are either nonstandard or considered incorrect in formal English. "Irregardless," for example, is often cited as a nonword because the correct term is "regardless." "Supposably" is similarly a misformed term often confused with "supposedly." Lastly, "ain't" is widely recognized as nonstandard or informal but is still understood in various dialects or informal contexts. Thus, "can't" stands out as the only option that is an accepted word in the English language.