[1] The term was originally defined as a countermine dug by defenders to prevent the undermining of a fortress's walls during a siege.
[2] More recently, the term has been used to describe the effects of very large bombs like the Grand Slam bomb, which are designed to penetrate next to a large target structure and create a camouflet to undermine the foundations of the structure.
A camouflet set describes a system used in the British Army for cratering tracks and other routes.
This void is then filled with a much larger charge, which is also tamped, and then blown when required to create a crater as an obstacle.
Because of the presence of high levels of toxic fumes from the explosive, including carbon monoxide, and the weakness of the soft earth overlying the cavern, camouflets are extremely hazardous to bomb disposal personnel.