It's an unknown object.

这是一个不明物体。

youdao

I have collided with unknown object.

我船和不明物体相碰。

youdao

Moreover, M. DE Rohan, quite unknown to himself, was an object of attention to the school-girls.

再说德·罗安先生还是那些寄读生注意的对象，他本人却并不知道。

youdao

Unknown flying object.

不明飞行物。

youdao

Unknown flying object.

不明飞行物。

youdao