noun
miniboss; sub-boss; mid-boss
Video game term for a boss enemy encountered partway through a stage or area, weaker than the main boss.
このステージの中ボスは意外と強い。
The miniboss in this stage is surprisingly tough.
noun
underboss
Colloquial term for the second-in-command of a criminal organization, often used in yakuza or mafia contexts.
あの組の中ボスはまだ若いが、かなり切れるらしい。
The underboss of that gang is still young, but they say he's quite sharp.