In Ruby and Perl 6 this has been called “splat”, and I think most people from
those communities will figure out what you mean if you call it that.
The Python tutorial uses the phrase “unpacking argument lists”, which is
long and descriptive.
It is also referred to as iterable unpacking, or in the case of **,
dictionary unpacking.
I call it “positional expansion”, as opposed to ** which I call “keyword expansion”.