Botón
A grass, a telltale, an informer — and, to older speakers, a police officer. An accusation, never banter.
Related lesson: Uruguayan Spanish: A Survival Guide.
Hear it in context
No le cuentes nada a ese, que es un botón.
Don't tell him anything — he's a grass.
Dejá de botonear a tus compañeros.
Stop telling on your classmates.
Mi abuelo todavía les dice botones a los policías.
My grandfather still calls police officers "botones".
What It Actually Means
A botón is someone who reports on their own side: the child who tells the teacher, the colleague who goes to management, the friend who repeats what was said in confidence. It is a charge of disloyalty rather than of dishonesty, and it is taken seriously at every age — Uruguayan and Argentine playgrounds run on it, and so do Uruguayan and Argentine workplaces. The verb botonear means to inform on, and botoneo the act itself.
Where It Comes From
Lunfardo, from the brass buttons on the nineteenth-century police uniform: the officer was a botón, and the person who did an officer’s work unpaid became one too. The police sense came first and the informer sense grew out of it, which is why the word carries the sting it does — it does not merely accuse you of talking, it puts you in the uniform.
How Natives Use It
As an insult, flatly. It has no affectionate reading, no ironic reading and no diminutive that softens it; sos un botón ends conversations. It is shared right across the Río de la Plata — Argentina uses it identically — and the police sense is now largely generational, held by older speakers while younger ones use it only for informers. Spain’s equivalent is chivato, Mexico’s soplón.
Common Pitfall
The ordinary noun has not gone anywhere: botón is still a button on a shirt and a button on a machine, and Uruguayans say it dozens of times a week without any of this in mind. Context does all the work, and it does it easily — the insult only appears with a person as its subject. What you should not do is try the word out as a joke on someone you have just met, the way you might risk boludo across the river. There is no version of botón that means “mate”.