Oversized Christmas Sweater

The concept of an oversized sweatshirt is something of a philosophical conundrum. How can a sweatshirt be "oversized" if it was made to exact specifications? For whom is this product "oversized" exactly? Any sweatshirt could be oversized if worn by a small enough person. Does an adult sweatshirt become oversized when placed over the truncated torso of Warwick Davis? Is a regular-sized sweatshirt undersized if James Corden has forced his sausagey frame inside it? Perhaps this is one of the great mysteries of the universe we'll never truly solve. Or, it's just a generic term for a ruddy massive jumper.