Can anyone please list me no-no words in American English ( By no-no words, I mean, the words that are not used by Americans)
Never walk into a pub in American and say "I want to bum a ***". This perfectly polite British request for a cigarette would have an entirely different meaning on the other side of the Atlantic.

Emotion: smile

Classic one Rommie, I quit fags last December!!!

I didn't think Americans used bollocks - WHAT, you don't have a cigarette? Bollocks, I wanted to bum a ***!
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I haven't figured out if the British expletive "bollocks" has made it across the Atlantic yet. There seems to be a rule on "Star Trek" that the characters can swear freely, but only in foreign languages, which is why you'll hear Captain Picard utter "***" from time to time, but will never say the same word in English. Miles O'Brien said "Bollocks!" once in an episode of DS9, which surprised me when I saw it. I did wonder if the American censors knew what it meant.

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My apologies, sankari, for not answering the original question. I got carried away with speaking in jest.

In my opinion there are NO words which are forbidden in American English. Once upon a time, it may have been true that there were words (such as "sidewalk") which were usable only on one side of the Atlantic, and other words (such as "pavement") which were usable only on the other side. I don't believe that is the case any more. This is the age of the internet. This is the age of satellite TV. Those old days are gone, and they're not coming back.

To clarify what I mean - traditionally, Americans don't use the words "lorry", "timber" or "motorway". (They say "truck", "lumber" and "freeway"). Nonetheless, if I was to write a novel about a hero who drove a lorry full of timber down a motorway, I guarantee that by the time my American readers got to the end of the novel they would know what those words meant, and will have added them to their vocabulary.

The main thing you want to watch out for is not vocabulary, it is spelling. When you cross the Atlantic, spelling rules change. This is unfortunate because, unlike introducing a new word to the vocabulary, the "wrong" spelling of a word does you a dis-service. It makes the reader think "that bugger can't spell". My advice here - set your spell-checker to American and leave it there. The vocabulary is not really a problem.