Noun
underboss (plural underbosses)
An assistant to the boss of a crime family
Serving as the Don's underboss is his oldest son, Santino. Source: Internet
John “Sonny” Franzese, the former underboss of the Colombo Crime Family, has died at 103, according to TMZ. Source: Internet
Sometimes an underboss may do this in penance to the oyabun if he wants to spare a member of his own gang from further retaliation. Source: Internet
Olsen would merit the title of underboss in the Arena pitch family. Source: Internet