... All of it? Does a bubble need to be confined to one vertical? It seems like The Bubble is just the sum of a bunch of other individual bubbles.

A bubble is a debt-fueled run-up in asset prices driven by over-optimistic projections of future fundamental value.

The housing bubble was people borrowing money (debt-fueled) to buy ever more expensive houses (rising asset prices) on the assumption home values would always keep going up (projection of future value).

'90s tech bubble was similar.

Where are you seeing that now? Which asset is over-valued?