erupt / irrupt
To burst out versus to burst in.
To erupt is to burst out: a volcano erupts; laughter erupts. To irrupt is to burst in. Irrupt is rare. If you mean a sudden outburst, write erupt.
Examples
Use The crowd erupted.
Use Deer irrupted into the yard.
Avoid The crowd irrupted. (If you mean they burst out, not in.)