No, not at all.
It refers to the design of every functional object or interface which is being used. That includes coffeepots, office doors, and toilet services. Not just websites, or mobile apps.

But the phenomena of UX attracted more attention when users started to rely more and more on screen interfaces, and building web interfaces became a common practice among designers, without the need for developers in every stage of their work.

* See the book below...
** These are called "Norman doors"...
Guess what: it's the same guy from that book...

But in his very own company, the Norman Nielsen Group, they also focus a lot on screen interfaces like websites, applications, and mobile apps.

Oorspronkelijk geplaatst op Quora: Does UX design only apply to websites?"