A sudden uncontrolled increase.
A sudden outburst.
A violent release of energy (sometimes mechanical, nuclear, or chemical.)
A bursting due to pressure.
The sound of an explosion.
A sudden intensification in activity.
An inflammation such as of tendons (tendonitis) or joints (osteoarthritis).
A sudden outbreak, outburst or eruption (originally of flame, but now used more generally of any violent activity or emotion).