What are some of your favorite engineering terms that you think others might not know?

I'm fully self-taught and every so often I come across terms for things I've experienced but didn't know there was a word for. I want to know what examples other people have.

I'll start. Three of my favorites are:

"That's an XY problem" to describe being asked for a solution when we should really be discussing the underlying problem. How do I do X because I'm trying to solve Y. I use this one in everyday life all the time.

"Heisenbug", a bug that is not reproducible while debugging or has its behavior change while debugging.

"Load bearing comment" is a comment that, if removed, causes the code to break. This doesn't happen anymore but it's a fun term for a terrifying concept.