Roger's Profanisaurus is a book published by Viz. The latest edition costs £4.49 from Amazon.co.uk

Roger's Profanisaurus is billed as "the king of swearing dictionaries" and there is some truth in this, as far as British English goes. It has come out available in several editions, each larger than the last, the latest containing 8000 or more rude words and phrases.

With over 8000 four-letter entries, Roger's Profanisaurus is surely the foulest-mouthed book ever to stalk the face of the earth.
- the back cover

Some of the entries were originally published in Viz. Viz's method for compiling this book seems to have been to collect entries from the Viz-reading public and collate them. To be pedantic, it's not quite a dictionary, more an utterly foul funny book. Many of the entries are improbable and disgusting, and are clearly inventions of the submitter, rather than actual common usage. That said, basically all of modern British obscene slang is explained, so the book will be useful to those needing to become familiar with it. The choicer of the invented phrases are passing into usage, especially among those dedicated enough to possess a copy.

Though some entries are excruciatingly funny, many are merely dull and dirty repetitions on a few basic themes. Do we really need hundreds of different disgusting phrases for each possible variation and combination of the following?

Apparently so, given the British psyche.

Many of the definitions are either not informative as a dictionary would be due to lack of content:
  Fudge packer: n. One who packs fudge.

Or are too obscure for a serious dictionary due to referring to other definitions:
  Red tie n. To finish oneself off with a sausage sandwich after having had enough of the cranberry sauce.

But in some entries the euphemism rises to admirable levels of repulsiveness:
  Nether eye n. That single unseeing eye, situated in the nether region, which cries brown, lumpy tears.

Some are just momentary wit:
  Kursk n. A giant dreadnought mouldering at the bottom of the pan.

And some are racist:
  Glaswegian Siesta n. a night in a police cell.

Or sexist:
  Hairy brain n. medic. The small, wrinkled organ, about the size of two plums, that governs a gentleman's thought processes.

The name of the book is a play on Roget's Thesaurus, and the foul-mouthed Viz character Roger Mellie.

The following editions have been produced:
Roger's Profanisaurus: 1998
Second edition: 2002
Profanisaurus Rex: 2005
Roger's Profanisaurus IV: The Magna Farta: 2007

There is a poorly maintained website at http://www.viz.co.uk/profanisaurus/profan_index.php