This makes no sense: in any actual RPG play, for instance, a player can declare "I go outside, find a patch of bare earth, and dig a hole in the ground with my fingers." How an the GM "refuse" to let that choice change the fiction, even if the GM didn't want the fiction to include such a thing?
By not letting the hole have a bearing on the game. Let's say you managed to dig a deep hole in the ground, using only your fingers. If the GM doesn't want the fiction to include the hole, then nobody falls in, traffic moves around it, nothing interesting is found at the bottom, no interesting events occur because of the hole, and not having the guards/mayor/local council/whoever stop/fine/arrest you for making it. You made a hole, but it means nothing to the game. And judging by some horror stories I've read, some GMs would go so far as to say things like "you sprain your wrist and can't continue digging" or even "no, you don't want to dig." Those would be
bad GMs, IMO, but it happens.
I was in a Changeling: the Dreaming game
very briefly that ended because of this sort of railroading. The straw that broke the game's back was when we went into the Dreaming to a land where, if you said a naughty word, a pie would appear and hit you in the face. The party contained a redcap. If you don't know from C:tD, redcaps are literally
always hungry and can eat anything (including heavy machinery). So the redcap's player was basically like, "sweet, free food!" and started cursing. The GM, who did not want this to happen, tried telling the player, "no, you're full, you don't want to eat anymore" and refused to allow the player to actually play his character the way it should be. This really angered the redcap's player and because of this and a few other incidents by the GM, the game folded in... the second session, I think.
If "railroading" is defined such that it only ever occurs if the GM literally vetoes players' action declarations for their PCs, it becomes a useless term, because it describes no actual play of a RPG.
You're misunderstanding what I mean. The GM has a story. You're not allowed to do things that go against that story. The GM fudges dice rolls or demands ludicrously high target numbers ("Nope, your nat 20 and +8 modifier isn't enough; you don't find any info" when you barely have to even roll to find out the plot of the story you're
supposed to be following), has NPCs be uncooperative or actively hostile, causes you to be attacked if you go where you're not supposed to, ignores character background and motivation if it goes against the story, nerfs abilities that would mess with the plot, and things like that.
That's railroading. Coming up with the world on their own, however, and telling you what you know about it isn't.