A sharp and experienced programmer who creates program code either many times faster than the average programmer or with much greater sophistication. Of course, the code must be bug- free or almost bug-free. The 10 factor is just an expression of "greater than" and not a hard and fast metric.
There Is a Difference
Like any profession, there are highly skilled workers and people who just get by. Some programmers can manipulate code like an experienced typist moves words around. However, to be a true 10x programmer, the code must be documented well enough for others to readily change if required in the future. See
coder and
programmer.