I too wrote a similar app for my personal problem and also served to be a good way to learn about kotlin and Android ecosystem. I also tried a rewrite in flutter and compose. The idea was to use select the word and then click meaning from context menu so that meaning occurs as notification and disappears in 15 seconds. I used Wiktionary as dataset source and app works offline.
I used rewriting as a learning experience. I found flutter to be simpler with respect to UI and state management compared to using XML by default for UI. Since mine was a crud app flutter was okay. I later found jetpack compose which has flutter like UI composition and I liked it better since I can access the existing Android library ecosystem too.
I loved that you built the context menu it's something I was thinking to. Congratulations.