Although application allows to get words from everywhere including web and different kinds of plain files it do not have abilities to recognize correct word form or sentence range. Sometimes translation services are good for particular area or language pair but really weak for another one.
Dictionaries created by people is great alternative in this case. A lot of professional translators and enthusiasts spent time to provide you with proven words and translations.
Here you will find the set of links for collections of supported dictionaries as well as dictionaries created by users of Lingo Quiz. If you think that your own dictionary has to be here, just export it and sent to me to publish it.
Abbyy Lingvo (DSL)
Abbyy Lingvo is a popular and powerful dictionary software with massive number of various dictionaries in LSD format. Using LSD decompiler you can get original human-readable DSL file to import it with application.
Lingvo Tutor (LTX)
Lingvo Tutor is a part of Abbyy Lingvo installation package which actually allows you to study words. It uses special XML format for dictionaries. To let Lingo Quiz recognize this kind of dictionary just rename it's extension from XML to LTX (Lingvo Tutor Xml).
Important: The previous version of Lingo Quiz 1.3 contains minor defect which breaks import of some Lingvo Tutor files. The workaround is to clean file from unwanted symbols. The easiest way to achieve this is to run the next PowerShell script (for Windows users) in console: (Get-Content "1.xml") -join "" -replace "\t" | Set-Content "1.ltx" -encoding unicode ; right after replacement of file names and pathes to them to your own.
Any Memo (DB)
AnyMemo is a similar program for Android which also allows you to memorise words. It was developed several years ago and now contains significant number of custom multi-purpose dictionaries.
Anki is another flashcard application for Android and other popular operating systems. Decks with cards can be obtained only with the help of this program which keeps them on SD card. After that you can easily import them.
Vocabilis is a desktop flash card application with quite good dictionary set. With Lingo Quiz you can import dictionaries and easily get mobile version!
Custom dictionaries (CSV)
Besides of mentioned external formats you can easily create your own dictionary in Excel and import it. Put words and translations in different columns and save it as Unicode (UTF-16) tab delimited file. Alternatively you can download this template to start with.
If you want to share your own dictionary feel free to contact me and I'll put it here along with your name.