Google dictionary is the new service from Google, that gives definitions for the words you search. When you search with a keyword a link “definition” appears on the blue bar above the search results. Google used to offer “define:word” parameter to get definitions, and now the dictionary is the natural extension of that.
Google dictionary although not as good as Answers.com, the later pulls lot of information for the query including Wikipedia articles etc. But for simple definitions Google dictionary is enough for most people.
It displays synonyms, definitions, related phrases for the word, and also web definitions, that is definitions from other places. You can star the words you searched using the star before the word. You can later see the starred words for your reference. It supports 28 languages as of now including most popular ones like English, French, Spanish etc. [Via Google OS]