fink on
phr. v..phr. v.. to tell someone in authority, like a teacher or the police, about something bad another person did. You usually do this to get them in trouble or to help yourself.
phr. v.. to inform on or betray an associate to an authority figure; functions as an intransitive phrasal verb followed by a prepositional object.
He decided to fink on his friends to avoid jail.
The gang members were worried that one of their own might fink on them to the detectives.
The informant was eventually ostracized by his community after it was discovered he had been finking on local activists for years.
highly informal and carries a strong negative connotation of betrayal.
this is a more colorful, slangy alternative to 'inform on' or 'tell on'; it is often associated with crime movies or schoolyard snitching.
He finked his brother.He finked on his brother.the verb requires the preposition 'on' before the person being reported.