Review for Merriam-Webster by Scorptilicus
Rated 2 out of 5 stars
While it does give you quite a few words, it is kind of annoying that you have to get an account for some of the more vague words. Definitions for those are all over the net at other free online dictionaries, so this one falls short of that.
This review is for a previous version of the add-on (20080326).To create your own collections, you must have a Mozilla Add-ons account.