《韦氏高阶》

otherwise：adv.

in a different way or manner

• All of the books had been burned or otherwise destroyed.

• 所有的书都被烧毁或以其它方式被损坏了。

• The women talked in the living room while the men were otherwise occupied.

• 女人们在客厅里聊天，而男人们则忙于其他事。

网友的句子中otherwise就是这种用法。

I told him I was otherwise engaged

我告诉他我在忙别的事。