Plot Railroad

In a dungeon crawl adventure, everybody knows what they're getting into. They want to go from Point A to Point B. The point of the story is to do exactly that. Most stories, though, aren't so strict. Adventurers go from town to town, meet people, explore locations. They may go from Point A to Point B in terms of plot, but they will take their sweet time getting there.

People often forget that the point of tabletop gaming is to have fun and be creative. If a GM feels like the players are highjacking the plot, then the plot railroad may be employed. In simplest terms, the plot railroad means that nothing that isn't planned goes on. The GM basically tells the players what to do, and if the players try to do anything else, they either get severely punished or outright told that their plans won't work.

"Plot railroad" is always a negative term. Stripping people of their freedom is the surest way to promote insurrection. Players either find themselves really fighting the GM, or just quitting out of boredom. When you only have the illusion of control, then the only point of being there is rolling the dice.

This is a major illustration of the difference between role playing games and non-interactive stories. As a reader of a novel or watcher of a movie, you know that you have no way to change things. But as a player, you are writing the story with the GM. If you read about a character in a situation where everything they tried to escape a situation failed, then you might interpret it as the author showing powerlessness. If the GM puts you in an inescapable situation, that's just being a dick.