Pronunciation: (ik-splō'zhun),[key] —n. 1. an act or instance of exploding; a violent expansion or bursting with noise, as of gunpowder or a boiler (opposed to implosion).
2. the noise itself: The loud explosion woke them. 3. a violent outburst, as of laughter or anger.
4. a sudden, rapid, or great increase: a population explosion. 5. the burning of the mixture of fuel and air in an internal-combustion engine.