Hard to say, really.........
But generally I'd class a diecast model as being:
Diecast (usually a zinc or aluminum alloy) for the major components and plastic for the details.
There are quite a lot of very fine diecast models being manufactured today - in the auto genre, the local model shop sells diecasts exclusively - Biante, AutoArt (the two are really the same), GMP and others make 1/18 scale models that are simply superb. There's also a couple of 1/6 scale GT40's (Mkl and Mkll) that are just amazing - working suspension and latches.
No longer can the diecast level of detail be compared to those horrible Burago things. But then again, for the price of a single example of some of those lovely models you could buy 20 Burago models. You get what you pay for.
Cheers
LeeTree
LeeTree