Once upon a time I built an iOS language translation/dictionary app which used Wikipedia as a back end. Basically, if you entered a word in language X and the Wikipedia version for language X had an entry, it could find the translation for that word in language Y by looking at the "this article in other languages" information in the source for that page. It was useful for finding translations or transliterations of terms that wouldn't commonly appear in standard dictionaries, like neologisms, brand names, or even just really obscure topics. Unfortunately it eventually got taken down from the App Store because Wikipedia's asshole lawyers didn't like that I used a serifed W in the logo even though I made it clear it wasn't an official Wikipedia product everywhere and I didn't have the motivation to "correct" my audacious use of an upper-case W which Wikipedia now apparently holds the copyrights to.

I still use this technique "manually" for finding translations when dictionaries, though. Wikipedia has a lot of information which isn't in a typical API-friendly format, but with a bit of regex there's some interesting possibilities.

If this sounds interesting, the Objective-C source is still available here: https://github.com/garrettalbright/wptrans You might also be able to find clones of it in the App Store since I know people were taking my source and republishing it back in the day, some even for a profit (mine was always free).