Exactly my point. I was just using CL as example because I think it would be hard to argue that it is not a Lisp yet the standard doesn't guarantee TCO.

> What is a lisp?

It's a very good question. I think PG sums it up quite nicely in "Revenge of the Nerds" [1]. Although, now that I'm thinking about it, I'm not quite sure there's any point in classifying something as a Lisp or not...

[1] http://www.paulgraham.com/icad.html