Ok, this word is a mind-boggler to me. First, let me use this word in a sentence as how an English person would use it.
"I just bought a new JUMPER today, and can't wait to wear it."
Question marks right? I mean, if you are from the states, and you were to hear this sentence you would be like, "huh? Your'e gonna wear what?" And then this vision will pop into your head:
Then you'll probably think that these English chaps are crazy in the head. Well....not exactly...maybe at times, but in this case no. First of all, people over here do not wear these type of jumpers....NOBODY would be able to wear one of these and look good in it...unless your first name is "Lady" and your last name is "GAGA."
But if you are a true Brit, you would know that in fact the word JUMPER refers to this ::
Yes. The word JUMPER in US english translates to sweater. Why? I have no idea Watson. But just remember, if a British person were to say they love your jumper, don't look at them like they were some psychotic weirdo, just look at your SWEATER and say, "thanks mate!"