A bubble is a floating ball of air. You can also blow a bubble with gum. If you’re in your own little bubble, you’re living in a fantasy, separated from the rest of the world by a thin layer of your imagination.
Whether you're blowing bubbles in the park or enjoying a bubble bath, those physical bubbles are made of liquid and gas. If something bubbles up, it comes to the surface. That can be an actual bubble or a just a feeling. A bubble can also be an idea that won’t work either because it’s a fantasy or because it’s an uncontrollable scheme, like a housing or economic bubble. The thing about bubbles is that they burst.