I don't know what else to call them but "generational" words - that is, words used by one generation, but not by another. Is there a better description? For example, my son, a millenial, and I were out and we saw this pretty woman. My son said, "She's thick," and I said, "She is not fat!" Apparently, however, now "thick" means being beautiful and nicely proportioned. That's new to me. Have you heard it used that way? What other words like this are there?

Loads and loads.

Young people's slang changes pretty well every generation, often faster. If a parent uses a slang word it is, almost by definition, no longer 'cool' so is out of date.

I know - but what are a few of them?

Have you heard of "thick" used that way?

Geoff tells me that a couple of years ago "sick" meant "beautiful," too. I am wondering if they are related.