I know that many today use "functional" to mean ML-derived languages but that definition is incorrect.
Lisps are not very much like Haskell at all, and have different goals. Which is why today's ML-centric worldview of functional programming so often forgets about them.
For many, functional programming is just as much about expressive type systems, purity, and immutability as is about robust first-class funtions and higher order functions.
Lisp is like the python version of Haskell (as compared to Java I guess?) It's a rough metaphor but I think it makes enough sense.