balloon
noun
A small, thin bag made of rubber or plastic that is filled with air or gas and inflated until it is round. Balloons are often used as toys for children, decorations for parties and events, or in scientific research.
Example
- Before the party, we decorated the room with balloons and streamers.
- The children were playing with water balloons on a hot summer day.
- The scientist used a balloon to measure the air pressure.