Bubble (noun)

1. A thin sphere of liquid enclosing air or gas.
2. An air or gas-filled cavity in a liquid or solid.
3. A small quantity of air or gas in a liquid or solid.
4. A dome-shaped covering, typically of glass, used to protect plants or furnishings from the weather.
5. A protective covering for a person or object.

Origin:

Late 16th century (as a verb in the sense "make a bubbling sound"): probably imitative.

Examples:

1. She blow a soap bubble.
2. A delicate bubble formed on the surface of the wine.
3. The roof was covered in a protective plastic bubble.
4. She was in a bubble of happiness.
5. The economy was in a speculative bubble.