I prefer the term linear or mostly linear Which is what you are describing. There is a clear start and end point and maybe a branch or two but it's a linear structure.
Railroad, to me, implies the players are unaware of the linear structure or that the DM is taking steps to keep then on the tracks/path.
Also, with a linear structure, the DM isn't fudging it's just that the direction of play is leading somewhere specific. BUT, the players are aware and if they want to go off the path, either they can (say start a different adventure) or can be convinced to keep going.
With a railroad, and the implied negative connotation, the players are unaware of the imposed end point. Generally, even if they want something else, they end up right where the DM/adventure intends instead of where they intended or where expecting.