In 1968, nurse Margo McCafferey defined pain as "whatever the experiencing person says it is, existing whenever and wherever the person say it does."
I don't think they've devised a scientific way of calculating pain. It doesn't have a unit of measurement. There's no way to predict how much pain a person will feel in a situation, or whether they will feel pain at all. Pain is unique to the person experiencing it.
That's my view on Writer's Block. Writer's Block is whatever the experiencing writer says it is, existinng whenever the writer says it does.
Many people do seem to experience Writer's Block. For whatever
reason, they're afraid to write at all. They are afraid of new words.
All the old words seem like too much crap to edit. They don't think in
stories, characters, plots. They stop trying to improve the craft.
Whatever, their reason, the writerly world takes it leave.
It's real to them, and it takes a supreme effort, and sometimes several years, to dig their way out.
A BLOCK TO WRITING
For me, Writer's Block is something that prevents writing and solely writing. If I'm too depressed to get out of bed, that's not Writer's Block, because that's stopping me from going to work, and from eating and from washing clothes, and from shopping, etc.
In addition, Writer's Block, to my mind, should prevent all writing. I've never been in a position where I'm incapable of writing anything in any genre. I might not be able to get words down on my novel today, but if I can write even so much as a limmerick, then I'm not blocked.
WHAT IS WRITING
The other reason I don't believe that Writer's Block exists for me is because of my wide definition of writing. Many people define writing as putting (new) words down on paper (/hard drive). But that's not all there is to writing in my mind. When I re-read my work, and edit it, that's writing. When I brainstorm characters or plot points, that's writing. When I let things ferment in my head for a week or a month, that's writing. When I read craft books, that's a part of my job as a writer. Ditto for reading, both in and outside of my genre.
If I'm unable to do any of these things, or I'm stuck in an endless loop of one of them, without moving onto any of the others, then I'd consider myself blocked.
How about you? Do you believe in Writer's Block? Have you ever been blocked?