That is a very interesting question chance22. I checked the online version of the Oxford English Dictionary (I think this is the concise version), and I do not see notations of singularity or plurality in noun entries (surely I must be mistaken, but I simply don't see the notation on the page).
In the online version of Merriam-Webster Collegiate, the term Olympic Games is plural and therefore takes a plural verb (e.g., are). I believe the unabridged version has a listing for the term Olympics, but I do not have a copy.
Out of curiosity, I did a quick Ngram search of Google books in both U.S. and British English. The usage patterns of "Olympics is" and "Olympics are" are remarkably similar over time (almost identical in U.S. English, and very close in British English, although the latter slightly favors "Olympics are").
There are differing opinions on the web. Here is a perspective from one grammar blog (among many others of course). In another page, the author uses "Olympics is" in her video description but then says "Olympics happen" a couple of times in her opening statements in the video, which just goes to show how tricky this one can be! :)
Student or Learner