noun
private detective; private investigator
A professional hired to investigate matters, often used in contrast to public police detectives.
彼は私立探偵を雇って、行方不明の妻を探してもらった。
He hired a private detective to search for his missing wife.
探偵 is a general term for detective, including both public and private. 私立探偵 specifically means a private detective.
Compound of 私立 (private) and 探偵 (detective).