I agree. There is nothing better than Google Definition Search when it comes to finding the meaning of a word. Type "Define" and the word Google will find the meaning out for you. Type "~" and the word, Google will find synonyms for you. This is one feature I use usually, as I am often short of words or find it difficult to understand some words. However, like I said in one of my posts earlier, Google has a structural limitation which sometimes makes it difficult to understand the word I want to understand. Google, as I understand, gleans meanings automatically and sometimes this makes it give you only half of the definition. What do I do with half of a definition? Obviously, I have to look elsewhere for the meaning. Now, how do I decide where I look from the hundred thousands of links Google gives me? That's how I stumbled upon OneLook.
OneLook is an Answer Engine. I think they link to Digital Dictionaries from every nook and corner of the world, gather meaning when you ask and present in a very structured manner. [So Wolfram|Alpha is not the first one to do that?] It gives you a categorized list of links so that you can look up the meaning based on what Category you have in mind. For example you search the word 'Home' The word 'Home' means different things in sports and computers. So when OneLook gives you the list and links to different dictionaries you can search based on what you have in mind at that point of time. If you have sports in your mind you can click on links under Sports Category. If you have computer in your mind, you can click on links under Computer Category.
The best thing I liked about OneLook is, whenever and where ever possible they give you the meanings. On one side of the search page they usually have Quick Definitions. These definitions come with sentences to show you how they are used in different contexts. Sometimes they give you a link to how the word is pronounced and sometimes how the word originated. They also have, usually, a list of similar words.