1. swelled or expanded rapidly to a much larger size
Usage: past tense of balloon
2. increased dramatically in amount or extent
Usage: past tense of balloon

Examples

• The hot air balloon ballooned as the burner heated the air inside.
• Her dress ballooned in the strong wind.
• The project costs ballooned beyond the original budget.
• His weight ballooned after he stopped exercising.
• The crowd ballooned to over a thousand people.
• The parachute ballooned open above the skydiver.
• Medical expenses ballooned during his hospital stay.