CBD is by no means Sydney-specific, just FYI, it’s a commonly used term in the English-speaking world. Due to the new-world situation of Australia’s cities, the CBD and downtown/city centre basically always overlap (I.e: there’s no ‘old town centre’ separate to the highrise district), so Aussies just refer to it all as ‘CBD’.

The term CBD isn’t used in the US, as far as I’ve ever heard. That’s probably why some commenters will be confused. I am only familiar with it because of a former coworker from Melbourne.

(Seattle is sort of similar in that there isn’t really an old town center, or rather it’s directly adjacent to the downtown highrises (Pioneer Square).)

It's not used in the UK either. Or rather, it's a technical term in human geography, probably used by geographers all over the world, but it's only in Australia that it's used in everyday language:

https://en.wikipedia.org/wiki/Central_business_district

I believe it's used in New Orleans. That's the only place I'd heard it before going to Australia.

Perhaps I should have said "widely used." :-) I have never been to Louisiana, but I've been to several states.

I never heard CBD until the first time I went to Sydney, but I understand it's common. I think in the US we tend to name our CBDs instead, like Chicago has "The Loop" and most places just say "downtown".

Isnt it used in Dallas sometimes? Dallas also has a separate Uptown from Downtown.