froth
n. uncountablen. a layer of bubbles on the surface of a liquid, like the foam on top of a coffee. It can also describe a situation where prices are too high and not based on real value.
n. a mass of bubbles on the surface of a liquid; by extension, a state of excessive speculation or inflation in financial markets. Often used in the idiom 'market froth' to describe unsustainable price bubbles.
The milk started to turn into froth as it heated up.
Investors were warned that the sudden rise in tech stock prices was just market froth that would eventually burst.
While the initial surge in housing prices seemed justified by economic growth, many analysts argued that the market was built on froth rather than a solid foundation of long-term demand.
From Middle English froth, frooth, froþ, likely a borrowing from Old Norse froða, from Proto-Germanic *fruþǭ; Old English āfrēoþan (“to foam, froth”) is from same Germanic root. Verb attested from late 14th century. Compare Swedish fradga.