The addon dictionaries are for the spell-check feature in Firefox. Those aren't like conventional dictionaries used to define what a word means.

well are there any Ican install on my toolbar to refer to & define words would the google one be O.K

Install a search engine for the online dictionary of your choice.
http://mycroft.mozdev.org/search-engines.html?name=dictionary

O.K.installed websters tryed a"synonyms" but it wanted me to install java scrypt before it would work I/ve seen dictionary's in the toolbar on other machines, but this in the search engine will do until i find out how to get the type Iwant