FOSS for Android

Owl for some reason won't display definitions and seemed to lack a considerable amount of definitions.

QDict requires additional apps so I didn't really both with it. Seems to be abandoned.

JADA no longer seems to function and is abandoned.

CollinsDictionary seems good for basic use. It requires the internet to function and can't search in a definition page. I don't believe it has sections for etymologies, though it had a neat pronunciation option. The definitions have the best layout I've seen so far being very easy to read. It seems to be abandoned and the most recent release hasn't been published to FDroid.

Spell4Wiki again would be good for basic use and has about the same features as CollinsDictionary. Includes etymologies and (I think) is a wrapper of wiktionary.

Aard 2 is my favorite at the moment and I think has the most features. Features I found useful in include search in definitions, bookmarks, offline viewing, translations, and histories. Although it can be used offline, it requires the internet permission to optionally load remote content. The setup was a bit difficult and I had to hop around on some websites to download the dictionaries.

QuickDic was pretty nice. It's very similar to Aard 2 but lacks alot of features. You can conveniently install dictionaries within the app, but for some reason the definitions aren't formatted which create a bunch of spaghetti words. Despite that, it was pleasant to use. I believe the app works without the internet permission after installing the dictionaries.