形容词

1. 前所未有的；空前的；没有先例的
If something is unprecedented, it has never happened before.

2. （质量、数量、规模）很高的，很大的
If you describe something as unprecedented, you are emphasizing that it is very great in quality, amount, or scale.

1. having no precedent
novel

e.g. an unprecedented expansion in population and industry