This app was mentioned in 9 comments, with an average of 2.33 upvotes
Knudge me: This app shows you random words with meaning, daily, and then ask you one of the shown word's meaning any time, after that.
I like this this app. Enjoy.
I know exactly how you feel. I found this app called knudge.me that helps you build up your vocabulary, and there's a section for more advanced words. I didn't really like the interface or format, but it could still be useful for you. Good luck!
Every day, I put up 12 notifications (maximum in the app setting) to recall particular words or quiz. Good app plus there are other quiz and games to play. Besides, you can pick which type of class you want (basic, medium, advanced). Highly recommend! :)
EDIT: Giving feedback would be helpful for the app to improve.
There's an app (Knudge.Me), it can really help you expand your vocabulary. I'd still suggest reading though, a lot of it actually.
Knudge.me app is great for improving English. It has a visual training method which helps understand and retain new words better.