One of the things I enjoy about erading Harry Potter is the occasional British-only english word. I just wish I could find the British versions of the books, that would be cool. Anyway, I found this page which lists a bunch with definitions. I knew all but 2. Here are some favourites:
BARKING. adj. Crazy. See also mad.
CORKING. adj. Excellent; splendid. Like spiffing. Often used sarcastically.
DODGY. adj. Evasive; suspicious; unclear.
NICK. v. To steal.
SPIFFING. adj. Excellent or first-rate (upper-class schoolboy slang, but often used in a sarcastic way to make fun of wealthy or pompous people). George Weasley, mocking Percy: "Absolutely spiffing." Like corking.
WONKY. adj. Shaky or weak. This word was actually used as a little pun in GOF. Hermione asks about a Quidditch Play that she calls the "Wonky Faint," which is really called the Wronski Feint. The pun suggests a weak move, while the Wronski play is really quite fast and aggressive.
Here’s the ones I didn’t know:
NOT A DICKEY (OR DICKY) BIRD. n. Reader "Dibble Helix" reports that this is Cockney rhyming slang for "not a word." Cockney is a London dialect of British English that includes colorful rhyming phrases, such as "Cain and Abel" for table or "dickey bird" for word (SOURCE: Cockney Online). A dickey bird is a type of small bird; one English dictionary indicated it was the hedge sparrow. In The Goblet of Fire, a character says in response to hearing any news, "Not a dickey bird."
LILO. n. An inflatable air mattress made of rubber or plastic. Name comes from a British market trademark for such a mattress. Used in Fantastic Beasts and Where to Find Them. "Dodgy Dirk" recalls a huge lizard that punctured his lilo while he was at the beach.