Name this python/ruby language construct (using array values to satisfy function parameters)

Question

What is this language construct called?

In Python I can say:

def a(b,c): return b+c
a(*[4,5])

and get 9. Likewise in Ruby:

Answer 1

I've been calling it "list expansion", but I don't think that's standard terminology (I don't think there's any...). Lisp in all versions (Scheme included), and Haskell and other functional languages, can do it easily enough, but I don't think it's easy to do in "mainstream" languages (maybe you can pull it off as a "reflection" stunt in some!-).