ˈ ̷ ̷ ̷ ̷ˌ ̷ ̷ ̷ ̷ noun
Etymology: under (III) + belly
: the lower surface of a body or mass
see a vast ruddy brilliance flash on the underbellies of clouds — Marjory S. Douglas
underbelly of a bomber
especially : a vulnerable area
Sicilian and Italian campaigns … could now be launched across the sea against the underbelly of Hitler's Europe — Sir Winston Churchill