That's true, but if you used that as the definition of "closure", then every subroutine that is in a lexical environment is a closure. That makes the term practically useless.

I think it's more useful to consider a closure to be a subroutine that closes around its lexical environment, and uses it to maintain state between invocations. It may not be as technically accurate, but it captures the meaning I think is most common, and definitely more useful.