Dictan - Dictionary Viewer

Dictan is a free Dictionary Viewer for Android which s .fdb and .zd/.zpak dictionary bases. These formats are open, so you may 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 's' section (plus many others available over the section of 'ZD resources'):

English Idioms
English Abbreviations
English Synonyms
Wiki
Other various dictionaries