Folks here are pretty loose about the terms, but I try to be a bit precise.

To me, vintage implies age, either based simply on more than X years old, though I draw the line about bikes based on whether they are older than Index shifting or not.

Classic, is more special, and I only use it for bikes that were considered special at the time, or great examples of their era, or were among the first of a new class of bikes, ie. an early mountain bike, or the first with front suspension. If we think about Bianchi, anything old enough can be vintage, but it also has to be Celeste to be considered a classic.

These are my opinions only, and I'm only a stickler about them among friends, because arguing about it is snobbish.