It's a corker (an excellent person or thing; something that closes a discussion, from the notion of putting a cork in it), a cracker, a whizz, a snozzler (if you're a New Zealander), even a piss-cutter (North American, naturally) or any one of numerous alternatives, all dated, located and explained.
It's also a must for anyone interested in the development of language. It covers everything, from The Body and its Parts (many, many words, some guaranteed to leave you gobsmacked (1985, British)) to Abstract Qualities and States. And it's well arranged by subject in the form of a thesaurus, with a convenient dictionary at the back.
But a word of warning: start to browse, and you'll find it unputdownable.