an underground explosion of a bomb or mine that does not break the surface, but leaves an enclosed cavity of gas and smoke.
2.
the pocket formed by such an explosion.
3.
the bomb or mine so exploded and causing such a pocket.
Origin: 1830–40; < F: lit., smoke blown in someone's face as a practical joke, MF chault moufflet, equiv. to chault hot (< L calidus) + moufflet presumably “puff, breath”; cf. Walloon dial. moufler to puff up the cheeks; 1st syll. prob. conformed to the expressive formative ca- (see cabbage1)