rat-trap, rat-catcher, ratter
one who has informed, one who has snitched, one who has ratted out
Его лу́чший друг сдал его нача́льству.
His best friend ratted him out to the authorities.
Она меня заложи́ла.
She ratted me out.
Он нас заложи́л.
He ratted us out.
