Google Search is offering a Word Coach feature for some which aims to test your knowledge of various words in the English language. The feature is reportedly popping up in both the Google app and on the Google mobile website sometimes after you search for a certain word, though users can also apparently cause Google Search to bring it up by searching directly for Word Coach or Google Word Coach. Multiple tests on a Google Pixel from both the Google app and Google Search through Chrome yielded no results, so it appears that there are other factors at play in terms of getting this to populate or it could simply be a small test.
If it does show up for you then you should end up getting five separate questions which will ask you different things like which words is most like a specific word that Google has displayed on screen. These will be accompanied by two possible answers and the user will be able to choose one accordingly to either get the right or wrong answer before moving to the next question. Worth noting is that the Word Coach questions you get will be determined by whether or not you are searching directly for Google Word Coach or for a word specifically. For example, if you search for the word prompt, you may get a Google Word Coach question asking you which of two displayed word is most like the word prompt, but if you simply search for Google Word Coach then you will be given a word.
It's not clear what Google's aim is for adding this feature in or how widespread it is. It doesn't seem to be a feature within the Google app or Google Search that has been rolled out to a large number of users just yet, so it could be something that Google has in testing. Whether or not Google ends up implementing this as a full-time feature going forward is also unclear. If you're looking to give this a try for yourself, you can attempt to search for various words in the Google app or through Google Search in Chrome or you can try searching for Word Coach to see if it comes up. Google is also reportedly adding a "level-up" function into the word coach that will increase the difficulty of the questions if they seem to simple, which may end up happening if you manage to answer a couple rounds of questions without getting a wrong answer.