1. To form or to produce round balls of air or gas; usually, inside a liquid: Water was bubbling or boiling in the kettle.
2. To flow with the quiet sounds of water moving over rocks: The brook was bubbling over the rocks and creating a wonderful sound.
3. To be very excited and happy: During the party, on the last day of school, the children were bubbling with excitement.
4. When emotions or feelings exist in a person without being shown to others: The winner of the prize seemed calm; however, his mother could see that her son was bubbling over with excitement about getting the trophy.