whistle blower(n = noun.person) whistle-blower, whistleblower - an informant who exposes wrongdoing within an organization in the hope of stopping it; "the law gives little protection to whistleblowers who feel the public has a right to know what is going on"; "the whistleblower was fired for exposing the conditions in mental hospitals"
is a kind of informant, source

blow the whistle, blower, boat whistle, factory whistle, glass blower, hand blower, police whistle, snow blower, steam whistle, tin whistle, whistle, whistle buoy, whistle for, whistle stop