snitch on (one)
To inform against a criminal or wrongdoer to a figure of authority. I'm afraid the mafia will make a hit on me since I snitched on them to the police about their money-laundering operation. Why would you snitch on me to the teacher like that?
snitch on someone
to tattle on someone. You wouldn't snitch on me, would you? Timmy snitched on his older brother.
snitch on
v. To disclose incriminating information about someone: She snitched on the coworker who had been stealing petty cash. He snitched on his little brother for breaking the vase.