deflagrate

Deflagrate combines the Latin verb flagrare, meaning "to burn," with the Latin prefix de-, meaning "down" or "away." Flagrare is also an ancestor of such words as conflagration and flagrant and is distantly related to fulgent and flame. In the field of explosives, deflagrate is used to describe the burning of fuel accelerated by the expansion of gasses under the pressure of containment, which causes the containing vessel to break apart. In comparison, the term detonate (from the Latin tonare, meaning "to thunder") refers to an instant, violent explosion that results when shock waves pass through molecules and displace them at supersonic speed. Deflagrate has been making sparks in English since about 1727, and detonate burst onto the scene a couple of years later.