fink

In its most basic sense, a "fink" is a derogatory term for a snitch or a betrayer. It describes someone who violates a group's unspoken code of loyalty for personal gain or to avoid trouble. Whether it's a student "tattling" to a teacher or a coworker reporting a colleague's small mistake to the boss, the label "fink" implies a person who is fundamentally unreliable.

Historically, the word also had a more specific and harsher meaning. In the early 20th century, especially in the American labor movement, a "fink" could mean a hired strikebreaker or a management spy. During bitter labor disputes, "finks" were seen as traitors to the workers because they crossed picket lines, passed information to management, or helped break a union's strength. That older history helps explain why the word still carries such a strong sense of selling others out.

In modern usage, the word also appears in the phrasal verb "to fink out." If you promise to help a friend move but cancel at the last minute because you do not feel like going, you might be said to have "finked out." In other contexts, something can "fink out" by giving up or stopping work, like an old car or a weak flashlight battery. Because the word is highly informal and strongly judgmental, it fits casual speech far better than formal or professional settings. Saying it directly to someone is likely to sound insulting and may start an argument.