R-Click search highlighted word in webpage with my choice of Search

[IconBoy]

Am using latest FireFox version and if I highlight a word, I can r-click on it and it'll Search Google for my highlighted word - very handy little feature!
On an iPhone, I saw a nice utility called WebSearch (http://justanotheriphoneblog.com/wordpress/2007/12/20/new-websearch-app-clever-timesaver-for-web-searches/) which allows you to add your own search sites for whatever word(s) you input. It then opens the browser to find it with that specific search (e.g. EBay, Wikipedia etc.)
Is there anything like this available as small coding "thing" for Windows users, whether FireFox or IE, when you start the browser? Or even better still, if I r-click on the highlighted word in a webpage, I can then get it to do the same thing WebSearch does?
Thanks for any help!

[lanux128]

if this is what you want, try this add-on: Dictionary Search.

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• http://dictionarysearch.mozdev.org/

[IconBoy]

Thanks very much. Is there anything that will allow me more than four searches?

[nosh]

Conquery replicates every search plugin you have installed to the context menu. 
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[lanux128]

so does Context Search, you can add as many search plugins as you want and the add-on will expand the context menu's 'Search for' item into a list of installed search engines, allowing you to choose a specific search engine every time.

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• https://addons.mozilla.org/en-US/firefox/addon/240