If someone is perspicacious, they are very good at judging people and situations — they see what is really going on, and they are usually right. It is a heavy, formal, bookish word. A teacher might write it in a report; almost nobody says it at the dinner table. It is not the same as being clever at school: you can be perspicacious about feelings and still fail a test. The Latin idea is “looking through.” Though actually, even native speakers mix it up with perspicuous, which means clear and easy to understand, usually of writing. One is about a sharp person; the other is about a clear sentence.

有洞察力的、眼光很準的（很書面）