informer
🇺🇸
/ɪnˈfɔːrmər/
🇬🇧
/ɪnˈfɔːmə(r)/
A person who provides information, especially about illegal activities.
The police arrested the criminals with the help of an informer.
警察はインフォーマーの助けを借りて犯罪者を逮捕した。