Definition & Meaning of "ratfink"in English

What is the origin of the term "ratfink" and how is it used?

"Ratfink" is an American slang term that emerged in the mid-20th century, combining "rat" (a longstanding metaphor for a traitor or informer) with "fink" (a derogatory term for a contemptible person or snitch) to label someone as a traitor, snitch, or informer. The term became popular in beatnik culture and later in hot-rod and countercultural circles, often appearing in comics, bumper stickers, and informal speech. It is clearly derogatory, used to express strong contempt for betrayal, disloyalty, or deceit, and is intended as an insult rather than neutral description.