A forced chamber explosion was a violent release of energy which could be caused by overloading certain energy-producing technologies.
In 2254, Number One set her laser pistol to overload, threatening a forced chamber explosion, as a means of convincing the Talosians that Humans would rather die than be kept in captivity. This, combined with information they had assimilated from the USS Enterprise's historical records, convinced the Talosians that Humans were too dangerous for their purposes. (TOS: "The Cage")
In 2368, a Romulan science vessel experienced a forced chamber explosion in their resonator coil during an test of an experimental interphase cloaking device, resulting in a member of their crew being phased out of reality and the deaths of all but seventy-three of their crew. (TNG: "The Next Phase")