This dictionary software has some nice features.
* All words are listed. You can see nearby words easily.
* Allow looking up all the words whose definition text contained a certain word.
* Allow looking up all the words that matched a pattern, which is very helpful for learning.
* It is free software, source code at https://github.com/baohaojun/BTAndroidWebViewSelection
* The dictionary data is also free, derived from GCIDE (http://ftp.gnu.org/gnu/gcide/).
* Other APKs can "share" a word for CrossDict to look it up.