v.1. To explode outward: The container was under so much pressure that it burst out.
2. To leave some place suddenly and forcefully: The doors from the bar opened and the crowd burst out. After school, the children burst out onto the playground.
3. To say something suddenly and loudly: The defendant burst out at the lawyers from the witness stand.
4. To start doing something suddenly: At the end of my story, everyone burst out laughing. The children burst out in song.