(idiomatic, usually with "on") To disclose information to the public or to appropriate authorities concerning the illegal or socially harmful actions of a person or group, especially a corporation or government agency.

One who reports a problem or violation to the authorities; especially, an employee or former employee who reports a violation by an employer.

(US, regional) The woodchuck.

(idiomatic, Southern US) To engage in idle conversational fantasies.

A tin whistle.

A high-pitched whistle, inaudible to humans, used to train dogs. / (figuratively) That which is understood only by a narrow demographic.

The action of a whistleblower.

(idiomatic) A small train station. / (politics) A brief stop on a campaign tour to make a speech or perform some other type of public electioneering.

(idiomatic) Extremely brief and hurried.

(politics, intransitive) To make a brief stop on a campaign tour to make a speech or perform some other type of public electioneering.