Degaussing. Most(all?) CRT monitors could do that. https://www.youtube.com/watch?v=PjO2vVaxIWM

Yes that was the word I was looking for. I gave away my last monster CRT 20 years ago and these things fade away from memory. Thanks!

Degaussing buttons were common on high-end CRT displays. They were always that fun!

In the mid-2000s, I worked at a place where we had several "decommissioned" Indys living a second life as Apache servers for some of our hosting clients - not uncommon in those days. We had one of the big 19" 4:3 CRTs on a KVM, too, and its weight put a noticeable if graceful curve in the MDF desktop on which it stood.

There was a time I had a 20” Apple behemoth on my desk in the open plan office. Degaussing it made the image on every monitor within 3 meters curl up in magnetic agony.

It was a lot of fun.

Like this?

https://www.youtube.com/watch?v=rSAnvHq_aFE

Yes but I could degauss mine when it was on. The image would rotate back and forth some 30 or 40 degrees which was fun.