A free app for Android, by Xynotec.

Want to get fluent in Italian or English? This helpful application by Xynotec is your gateway to acquire that fluency. 

It’s a dictionary that carries 134176 English to Italian words and 70814 Italian to English words, all with integrated pronunciation, that you can access offline. That way, if you’re reading at a park or somewhere without an internet connection, you will still be able to look up the translation of a word.

Apart from that, the app also lets you save your favorite words and you can view your search history so you can go back to learning them anytime. 

It also offers voice input and Google translate support but these require internet connection.