If you've ever asked a Brit for a bathroom and got a room with only a tub in it (use 'loo' or 'toilet') you know what I mean. So for anyone planning to go to England - here are some terms that are NOT what you might think when you hear them:
Poofter - An extended version of the word "poof", this is how you could refer either to a gay man or to a guy who is being a bit of a nancy boy or woofter.
Bum chum - Another name for a gay man.
Cake hole - your mouth
Pussy - A cat, as in "pussy cat". So if a Brit asks if you have seen her pussy, try to keep a straight face.
Hash - The thing you call a pound sign!
John Thomas - A man's penis. Too bad if this is really your name, just stay out of England.
Knock up - This means to wake someone up.
On the piss - If you are out on the piss, it means you are out to get drunk.
Pissed - This is a great one for misunderstanding. It means drunk, not mad!
Clever dick - This is a bit of a wise guy, not performing tricks with certain parts of the body!
Wanker - This is a derogatory term used to describe someone who is a bit of a jerk.
Blow me - It is simply an exclamation of surprise, short for "Blow me down", and is even used in polite company (so don't be shocked).
Bung - to throw; or a bribe
Potty - This isn't just the thing you sit a toddler on - if you are potty it means you are a little crazy.
Cock up - A cock up means you have made a mistake.
Diddle - To rip someone off or to con someone is to diddle them.
Fagged - Means you are too lazy or tired to do something.
Fanny - Be careful! This is the word for a woman's breasts! It is a bit rude, and you certainly don't have a fanny pack!
Blower - The blower is the telephone, before you get too excited!
Box - Just the TV
Scatty - Otherwise known as scatterbrains.
Power point - No not Microsoft; This would be an electric socket in the US.
Boffin - This is the word for a nerd.
Scrubber or Slag - This is a nasty way of referring to a loose woman.
Thick - If someone is thick it means they are stupid.
Septic - Try not to be offended, but this means an American.
Beefeater - This is the name given to the guards at the Tower of London (and gin!)
Big girl's blouse - This is a nice way of saying someone is a wimp.
Up the Duff - My personal favorite; If a woman is up the duff it means she is pregnant.
Thanks to The Best of British at Effingpot for the above help!