rat fink(redirected from a rat fink)
1. One who is regarded as a traitor for reporting criminal activity to the police. Primarily heard in US. The gang was determined to find the rat fink who told the police about their illegal activities.
2. An unpleasant person. Mike is such a rat fink that I can't even stand being in the same room as him.
n. an informer. (see also rat.) That guy is nothing but a rat fink. A dirty squealer!