Much not slang, just Standard British English, the Queens English!
Not only is the presentation of words random, and there doesnt seem to be a way to look up the meaning of words, much of the so called slang is standard British English, as one finds in "The" dictionary of English, the Oxford English Dictionary. Very sloppy and not worth the time, and likely to cause embarrassment to anyone who tries to use it as a language guide in the UK. Horrible!
Lonnie the Pooh about
British Slang! New Dictionary of Urban Slangs Quiz, v2.2.2