'Simple English Wiktionary':
Wiktionary in Simple English is an online dictionary that uses simpler words so it is easier to understand. There are about
20,500 words. To find a word, type it into the "search" box. For example, if you want to know what "dictionary" means, type "dictionary" into the box and press the 'search button'.
http://simple.wiktionary.org/wiki/Main_Page (click this link to go to Simple English Wiktionary)