The term "private dick" is a slang term used to refer to a private investigator. However, there are several other synonyms that can be used instead of this term. For example, a PI can be referred to as a private eye, gumshoe, sleuth, detective, investigator, or inquiry agent. These terms are used interchangeably and vary based on the region, industry, or context in which they are used. Regardless of the synonym used, a private investigator is a professional who works to gather information for their clients, solve cases, and provide expert advice. They are an essential part of the legal system and often work with law enforcement to bring criminals to justice.