Most chemists are secret pyromaniacs, so the term deflagration is very familiar to me: it is a manner of burning which is just below an explosion in its intensity. It does not cause a shot noise, but rather a "swishing" noise. This is generally brought about by an oxydizing agent which is mixed with the combustible material, as mentioned in the example "nitre" plus charcoal. If the same mixture is enclosed in a shell and ignited, it causes an explosion.