Google is testing the ability to click on a word in a featured snippet within Google Search and define that word. You can also copy the word, if you want. I think this is a Google Search test and maybe not a Chrome test.
This was spotted by Punit who posted a video of this in action on Twitter, here is a screenshot of this video:
Here is the video embed:
The reason I think this is a Google Search test and not a Chrome test is because he lost his Google session and was not able to trigger it again. I can be wrong and this might be a Chrome test and not a Google Search test.
Google is also testing this in other areas of the search results:
Forum discussion at Twitter.