Script Summary: Hold down the alt key and double click a word (or select it) to bring up the definition from Dictionary.com. Hold down control and alt and select a phrase or word and then let go of the mouse to launch a window with the Wikipedia article for that word/phrase.
Double clicking a word in Firefox is the same as selecting it. This script adds a mouseUp event to the document so that when the mouse button is released and the alt key is held down and the current selection is of a word longer than 2 characters a window opens with the definition of that word courtesy of Dictionary.com.
It also includes links to lookups of the word with Google, Urban Dictionary and Wikipedia.
