In the old Marvel Universe books and the pen & paper RPG, people who obtained "innate" powers (not born with them), ie not built from technology or addons, were called "altered humans". So Spiderman, Captain America, Hulk, etc., were altered humans while the xmen and anyone else born with their powers were mutants. Don't know what the explanation for Scarlet Witch and Quicksilver will be, but if they're born with their powers in the movie they won't be able to use the term "mutant" from what I understand.
