Sometimes you will find life a lot more easier, if you can search some words by select them and then using your Right-Click menu instead of type them into your search bar yourself!

    DictionarySearch Extension is just the tool you need to do so! First, go and install DictionarySearch extension! After restarting your Firefox, go to Add-ons and click the "Option " for DictionarySearch extension. you would find something like the one below, except that yours are all empty! Fill them with your desired search engine! Dont know how to do it? It is very easy!

1. Go to your  desired search site and type "ok" and do a search!(Example: dictionary.com )
 2. Copy the URL in your address bar (example:http://dictionary.reference.com/browse/ok) and paste it into the "URL:" text box in your "Option" window, then replace "ok" without the quotation mark.

3. Type "Search XXX for "$""(example:"Search Dictionary for "$""), notice that there are quotation marks this time.

4. Click 'OK", you are done! 

 Here is my "Option" window:

Dictionary 1

Text: Search Dictionary for "$"

URL:http://dictionary.reference.com/browse/$

Dictionary 2

Text: Search Ciba for "$"

URL: http://www.iciba.com/search?s=$&lang=gb2312&t=word&sourceid=mozilla-search

(This one is a little bit tricky, because it evolves text encoding. btw, ciba.com is a Chinese Online Dictionary provided by Kingsoft ) 

Dictionary 3

Text: Search Wikipedia for "$"

URL: http://en.wikipedia.org/wiki/$ 

Dictionary 4

Text: Go to "$"

URL: $ 

On the above, it is the result!