She had known Max for some years now, but he was still pretty much an unknown quantity.

她现在认识马克斯也好几年了，但是他仍然是个大大的未知数。

《柯林斯英汉双解大词典》

The Frenchman was an unknown quantity when he arrived in north London back in 1996.

1996年，当他初到北伦敦时，这个法国人还只不过是个未知数而已。

youdao

Are an unknown quantity.

对于他们来说是一个未知的组合。

youdao