Description:
if you're looking for the meaning of a new word in English language, these sites do not give you the meaning only, but also they show you the explanations for these words and their parts of speech as well, in addition to putting these words in sentences to make them more understandable and clear.
Links:
http://oxforddictionaries.com/
http://dictionary.cambridge.org/
http://www.thefreedictionary.com/
http://www.merriam-webster.com/home.htm
http://dictionary.reference.com