The phrase "giant bubble" refers to a situation where something, like an idea or a market, grows really big and becomes unstable or unsustainable, similar to how a soap bubble expands before it pops. Full definition
Today we've been finding out how to make giant bubbles. (science-sparks.com)
Making homemade giant bubbles has been on our to - do list for a while, but we've been waiting for the perfect weather conditions. (happyhooligans.ca)
Jets of plasma stream out of the black hole close to the speed of light, and some distance away, they inflate into giant bubbles of hot gas. (ibtimes.com)