A private detective, also known as a private investigator, is a professional who investigates and gathers evidence on behalf of their clients. PEEPER is a 6-letter solution to the term PRIVATE DETECTIVE, and it refers to someone who secretly watches or follows someone else. SNOOP is a 5-letter solution to the term PRIVATE DETECTIVE, and it refers to someone who investigates or looks around in a nosy way. TRACER is a 6-letter solution to the term PRIVATE DETECTIVE, and it refers to someone who follows or tracks down a person or thing.