The OED is considered the closest thing to the definitive record of the English language that there is. They claim to be the definitive record. However, without a British equivalent of the Académie française (whose judgements are not even binding), it is difficult to argue a definitive document.
Nevertheless, it is the best thing we have. I had never taken a look at it before, but the depth of information is astonishing. For each word, sometimes over multiple entries, it contains the spellings, forms, frequency in current usage, etymology and a long list of definitions with extensive citations for each. The definitions are followed by a list of phrases, compounds, and derivatives. There is a thesaurus entry for each definition.
In short, it is difficult to image a more complete reference on the English language.
Why do I mention this? Because it turns out that it is totally free!
I have used Dictionary.com for many years because it is easy and for a free product, it is very good. It too contains pronunciation, synonyms, and a limited amount of auxiliary information. It was perfectly adequate for what I wanted. The idea of paying the £215.00 a year subscription to get access to the OED was clearly laughable.
However, it turns out that we all have the ability to access it for free. The OED website allows you to log in using your public library membership number. They say almost every library subscribes, but given my Leeds Library card worked, it is hard to imagine any council cheaper than Leeds.
I registered my library card about eight years ago and it was still valid. It is well worth digging out of the wardrobe. Or, if you do not have one, pop down to your local library and register for one. Once you do, you can access the service online at home, or from anywhere else.