A word that is particularly confusing is "momentarily", which to us means "for a short while" or "briefly" but to them means "in a short while", where we'd say "shortly" or "presently".
That reminds me. I was pretty sure I understood what people meant by "now", until I moved to south Wales. There it refers to a point of time, possibly the present, but also possibly some time in the future, and often with an added phrase to add precision e.g. "I'll do it now in a minute", "I'll do it now this afternoon", "I'll do it now tomorrow morning". "I'll do it now" on its own can mean "I'll do it after I've had this cup of tea and a biscuit, and read the paper, and done numerous other things, but it's definitely on my things to do in the fullness of time."