E-E Dictionaries, I usually use dictionary.com, or merriam-webster.com, on a cellphone I use these two websites' apps. For C-E I use mdbg.net or for a cellphone, I use pleco.

Growing up I always used dictionary.com when I needed to look up a definition.

http://diccionario.reverso.net/

USA folks will tend to promote US dictionaries, and British folks will tend to promote UK dictionaries. Quite understandable. "Best dictionary" is a matter of personal opinion. Oxford University Press (OUP) is the largest university press in the world, and the second-oldest , after Cambridge University Press (founded 1534). http://www.oxforddictionaries.com/ Gives both UK and USA spellings, definitions, pronunciations and examples.