I found the word ‘misunderestimating’ in the article written by Peter Catapano under the caption 'Don't stop believing' in Opinionator’s Column section of New York Times (April 29). The word is not ...
Google finds 52,000,000 matches for ain't but non-natives simply can't look up this word. Wiktionary isn't helpful. Is it some kind of 'wildcard' for "am/is/are not"?