This is not new, but it's new to me. You're likely aware that if you double click on a word on the online version of the New York Times, the definition pops up. Well, it seem that the NYT keeps track of which words folks pop up most and the list, as of last June is available here. The top 10 lookups per use are:
The only ones I knew were bonobo, shibboleth, and adenoidal. I've looked up epistemological many time, but I still can't say I really know what it means. Do you fare any better than me?