> Becoming a professor is called getting your 'chair' isn't it?

No.

> I don't know any professors who don't also have tenure - that seems a contradiction in terms to me.

Assistant professors generally do not have tenure, and at some institutions being an associate professor or full professor is no guarantee either.

> But if you don't know what I mean we're probably talking about different things and possibly talking at cross-purposes.

I know what you mean; you're just incorrect and spreading misinformation based on your limited experience.