Stool pigeon and Tipster

Stool pigeon noun – A person who provides information about another's wrongdoing.

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Tipster and stool pigeon are semantically related in knowledge topic. In some cases you can use "Tipster" instead a noun phrase "Stool pigeon", when it comes to topics like informer to police.

Tipster noun – One who sells advice about gambling or speculation (especially at the racetrack).

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Stool pigeon and tipster are semantically related in knowledge topic. You can use "Stool pigeon" instead a noun "Tipster", if it concerns topics such as sneak, gossip, informer, reporter.