Dictan is a free Dictionary Viewer for Android which supports .fdb and .zd/.zpak dictionary bases. These formats are open so you may download lots of free .zd dictionaries handbooks and encyclopedias from the Internet or create your own ones. Put .zd bases into /sdcard/dictan/ and they are ready for viewing! All extra info and the tools to create your own dictionaries are available at WWW.SOFTEX.INFO

The web-site also has the following free dictionaries in the 'Downloads' section (plus many others available over the section of 'ZD resources'):

English Wikipedia 2011
Russian Wikipedia 2015
Chinese Wikipedia 2015
Ukrainian Wikipedia 2010
Encyclopedia Britannica
Merriam-Webster
English Idioms
English Abbreviations
English Synonyms
Other various dictionaries