1. inflatable rubber or plastic bags filled with air or gas, often used for decoration or entertainment
2. large bags filled with hot air or gas used for flying

1. to swell or expand rapidly in size
2. to increase quickly and dramatically

Examples

• The children released colorful balloons into the sky.
• Hot air balloons floated peacefully over the valley.
• She tied balloons to the birthday chair.
• The debt balloons if you only make minimum payments.
• His weight ballooned after he stopped exercising.
• The project costs ballooned beyond the original budget.
• Weather balloons collect atmospheric data.