"We have really everything in common with America nowadays except, of course, language"
- Oscar Wilde, The Canterville Ghost (1887)
"England and America are two countries separated by the same language"
- George Bernard Shaw (or possibly Winston Churchill, opinion differs)
(Note: this is an ever growing list the longer we live here in the United States, I'm adding to it almost daily).
I've put the American word first, followed by the UK English translation or an explanation.
House and Home
Comforter = Duvet (though rather interestingly, you can put a white comforter inside a 'duvet cover')
Nightstand = Bedside Cabinet
Loveseat = 2 seated settee/sofa
Sofa = 3 seated settee
Yard = Garden
Trash/Garbage = Rubbish
Trash can = Waste bin
Plastic wrap = Cling film
Pail = Bucket
Binder = Folder
Eraser = Rubber
Trash can = Bin
Shopping cart = Shopping trolley (or simply cart = trolley)
Store = Shop
Ground Floor = 1st Floor
Lobby = Ground Floor
Elevator = Lift
Pants = Trousers
Intimates = Underwear
Jumper = can be either a pair of dungarees or more commonly a pinafore dress
Sweater = what we Brits call a jumper
Undershirt = Vest
Tennis shoes/Sneakers = Trainers
Pantyhose = flesh coloured tights, in the US 'tights' refers to only to thick coloured tights particularly worn by Robin Hood and Errol Flynn ;)
Biscuit = a plain scone, often eaten with sawmill gravy
Cookie = what we Brits call a biscuit!
Sawmill gravy (also just called gravy) = a sort of Béchamel sauce but with tiny bits of meat in it (here's how to make it from the Food Network)
Canadian Bacon = a thin pressed ham
Eggplant = Aubergine
Garbanzo beans = Chickpeas
Cilantro = Coriander leaf (in the USA, coriander refers to the seeds only)
Rutabaga = Swede
Zucchini = Courgette
Scallion = Spring Onion
Napa Cabbage = Chinese Leaf
Jello = Jelly
Jelly = Jam
Powdered sugar = Icing sugar
TV and Film
Season = Series
Movie Theater = Cinema
Driving and Vehicles
Pavement = the actual road or tarmac
Sidewalk = Pavement
Yellow light = Amber light (on traffic lights)
Stop lights = Traffic lights
Semi = Lorry
Truck = SUV with 4 seats
Pick-up truck = SUV with 2 seats
Mini-van = an MPV or People Carrier
Travel Trailer = Caravan
Windshield = Windscreen
GPS = Sat Nav
Emergency Room = A&E (Accident and Emergency)
Acetaminophen (generic name) usually seen as the brand name Tylenol = Paracetamol (generic name)
Drugstore = Chemists
Sunscreen = Suncream
British words or phrases that Americans just don't understand
Getting 'told off' (when a parent or teacher reprimands you)
Something being 'in bits' or 'bits and pieces'
'Can't be bothered' (not wanting to do something because it doesn't interest you or you're tired)
'The other day' (Americans don't understand this concept at all, they always refer to the specific time, so 'yesterday' or 'last week' or '2 days ago' - they don't have a phrase they use for a short time ago in the past)
'Brilliant' not a word used in a America. It is used by Brits to express that something is excellent. And 'bloody brilliant' is even better (the word 'bloody' as a swear word again is not in use at all in the US).
# in Amercia this is a 'pound sign', but it can also be known as a hash
. in America this is a 'period', in the UK it's a 'full stop'
Much confusion arises over numbers. If you have a number eg. 6950, Americans will say this is "69 hundred 50", Brits will say this is "6 thousand 9 hundred AND 50". It has taken me nearly 2 years to remember that when Americans say something hundred it's actually what I think as something thousand. We Brits like to add an 'AND' somewhere within the big numbers, so 2305 would be "2 THOUSAND 3 HUNDRED AND 5" (I think Americans would simply say "23 hundred 5". This difference was 'great fun' when we were moving house and caused lots of confusion.
Nought - say this for 0 if you really want to confuse an American, they have no idea what nought is, and instead use the word zero.