Cooking off (or thermally induced firing) is unfired weapon ammunition exploding prematurely due to heat in the surrounding environment. The term is used both for detonation of ammunition not loaded into a weapon, and unintended firing of a loaded weapon due to heating. A fast cook-off is a cook-off caused by fire. A slow cook-off is caused by a sustained thermal event less intense than fire. A cooked-off round may cause a sympathetic detonation of adjacent rounds. Insensitive munitions are designed to be less vulnerable to accidental firing induced by external heat. Artillery.
https://en.wikipedia.org/wiki/Cooking_off