Aard Dictionary for Android is a free, fast, easy to use word lookup program that

• looks up words fast even with huge dictionaries like English Wikipedia
• looks up words in multiple dictionaries in multiple languages without switching
• works great as offline Wikipedia reader
• uses same efficient, highly compressed dictionary data storage format as the desktop version
• lookup words from FBReader and CoolReader

Links:

• User guide
• Download dictionaries
• Report issues

Screenshots: