an occasion when a plane falls in the sky with its nose (= front part) downwards and its tail (= end part) spinning in a very wide circle （飞机头朝下下坠时的）尾旋，尾螺旋
The plane went into a tailspin. 飞机打着尾旋开始下坠。
2
informal an occasion when something or someone suddenly gets into a very bad state （忽然陷入的）困境，混乱
sending the nation’ s financial markets into a tailspin 使该国的金融市场陷入混乱