n.下腹部；易受攻击的地带

The underbelly of the plane was seriously damaged in the emergency. 飞机的腹部在这起事件中严重受损。

The sick woman complains on acute pain in the underbelly. 患病妇女说她下腹剧痛。

The trade deficit remains the soft underbelly of the US economy. 贸易赤字仍是美国经济的软肋。

The underbelly of the club at the minute needs to be slightly stronger. 这是俱乐部现在的弱点，而我们不得不变的更强壮些。