A whistleblower is a person who raises a concern about alleged wrongdoing occurring in a government or governmental entity or a private or public corporation or an organization or agency that is expected, by the public at large, to be operating within the bounds of the law.
The alleged misconduct may be classified in many ways; for example, a violation of a law, rule, regulation and/or a direct threat to public interest, such as fraud, health/safety violations, and corruption. Whistleblowers may make their allegations internally (for example, to other people within the accused organization) or externally (to regulators, law enforcement agencies, to the media or to groups concerned with the issues).
Additional meaning of Whistle Blower:
Whistleblowers frequently face reprisal, sometimes at the hands of the organization or group which they have accused, sometimes from related organizations, and sometimes under law.