Yes; a SERP is a Google search result page. It's the most important acronym in SEO.

I don’t remember never ever hearing it and I’ve been in the industry for some time

Huh. I've never been in the industry, but noticed "SERP" at least 15, maybe 20, years ago and have remembered it since.

(If I were writing something to be published, though, I would write "search-engine results page" instead of "SERP".)

You've been in the SEO industry for some time and never heard SERP?

The web programming industry, not the SEO industry

There is actually only very little overlap between SEO and web development. Web developers should know some basic technical SEO but you'd be surprised how much knowledge is in the SEO industry that doesn't overlap at all with development. So, it's not too surprising you don't know what SERP is. Web devs might think SEO just means fast load times, proper markup, meta tags, etc but that's only the very surface

You can't be serious.

The word SERP feels like a bit of a shibboleth for SEO-people. They seem to take it for granted, the rest of the world just looks puzzled when they hear it.

I had to look it up.

SERP: Search Engine Results Page

Unintroduced acronyms should always be avoided.

Depends on the audience-acronym pair. I don't think HTTP needs an introduction in a technical article, OTOH (on the other hand ;) ) a general newspaper should probably expand HTTP but not WWW.

Perhaps a stroll through your own comment history (or the comments of any other HN (hacker news) user) would illuminate a lot of places where acronyms are used without introductions. TBH (to be honest) though, I'm not sure if every one of those should always have one or sometimes not.

As English speakers we often take for granted acronyms such as DB or even USA. For foreigners these can also be inscrutable.

On HN I'm used to SE meaning Software Engineer so I came up with "Software Engineer Ranting Board" before asking Google to give me the SERP that would provide me with the true meaning of SERP.

An all-too-common occurrence in HN comments as well.

Not the OP, but I thought it was well known.

That said, I do a lot of SEO work.

Still, it should be best practice to define any acronym or initialism the first time you use it