WordReference used to have all the Collins dictionaries available online, for free browsing. I was the main dictionary computing guy at Collins when this deal was made, and it was pretty cool to have a good, non-US English dictionary on the web.
I gues the money has run out, as the Collins data has disappeared, and the English dictionary is derived from WordNet. While I think that WordNet‘s a worthy project, it doesn’t quite compare to the Collins English Dictionary.
Oh well, it was good to know you, WordReference.