Going to the UK? If so, read this so you can understand what people are saying.
On the job - If you are on the job, it could mean that you are hard at work, or having sex. Usually the context helps you decide which it is!
On the piss - If you are out on the piss, it means you are out to get drunk, or to get pissed.
On your bike - A very polite way of telling someone to f*** off.
One off - A one off is a special or a one time event that is never to be repeated. Like writing this book!
Owt - This is Yorkshire for anything. Similarly nowt is Yorkshire for nothing. Hence the expression "you don't get owt for nowt". Roughly translated as "you never get anything for nothing" or "there's no such thing as a free lunch".
Pants - This is quite a new expression - I have no idea where it came from. Anyway, it is now quite trendy to say that something which is total crap is "pants". For instance you could say the last episode of a TV show was "total pants".
Pardon me - This is very amusing for Brits in America. Most kids are taught to say "pardon me" if they fart in public or at the table etc. In America it has other meanings which take us Brits a while to figure out. I thought I was surrounded by people with flatulence problems!
Parky - Either short for Michael Parkinson, a famous chat show host, or more likely a word to describe the weather as being rather cold!
Pass - This means I don't know and comes from the old TV show, Mastermind, where contestants were made to say "pass" if they did not know the answer to the question.
Pavement pizza - Well here the pavement is the sidewalk and a pavement pizza is a descriptive way of saying vomit. Often found outside Indian restaurants early on a Sunday morning.
Peanuts - I hated one of my summer jobs as a kid because it paid peanuts. The full expression is that if you pay peanuts, you get monkeys. It is a fairly derogatory way of saying that manual labour doesn't need to be bright and doesn't need a lot of pay. Typically these days peanuts means something is cheap. For example we would say the petrol in the USA is peanuts or costs peanuts. Compared to our prices it is.
Pear shaped - If something has gone pear shaped it means it has become a disaster. It might be preparing a dinner party or arranging a meeting, any of these things can go completely pear shaped.
Piece of cake - I remember saying it's a piece of cake in front of one of my American friends, who then started looking around for the cake! It means it's a cinch!
Pinch - This means to steal something. Though when you say "steal" it is a bit more serious than pinch. A kid might pinch a cake from the kitchen. A thief would steal something during a burglary.
Pip pip - Another out-dated expression meaning goodbye. Not used any more.
Piss poor - If something is described as being "piss poor" it means it is an extremely poor attempt at something.
Piss up - A piss up is a drinking session. A visit to the pub. There is an English expression to describe someone as disorganised which says that he/she could not organise a piss up in a brewery!
Pissed - This is a great one for misunderstanding. Most people go to the pub to get pissed. In fact the object of a stag night is to get as pissed as possible. Getting pissed means getting drunk. It does not mean getting angry. That would be getting pissed off!
Pissing around - Fooling about, in the sense of messing around or making fun or just being silly. Not terribly polite.
Plastered - Another word for loaded. In other words you have had rather too much to drink down your local. It has nothing to do with being covered with plaster though anything is possible when you are plastered.
Porkies - More cockney rhyming slang. Short for "porky pies", meaning "pork pies". Rhymes with lies. My Mum always used to tell me I was telling porkies! And she was right!
Porridge - Doing porridge means to serve time in prison. There was also a comedy TV series called Porridge about a prisoner starring Ronnie Barker of The Two Ronnies fame.
Clancy's comment: There ya go. Pip pip, folks.