Metagaming is a situation in a tabletop roleplaying game where your GM doesn’t want you to do something so arbitrarily decides your character can’t do that because they need pre-requisite knowledge to be able to do that despite not putting any real mechanism in place to have that pre-requisite knowledge beyond perhaps an even more arbitrary knowledge roll which most of the classes in the game forfeit because the games skill systems are so particularly asinine.
Murder hoboing is a situation in a tabletop roleplaying game when your GM doesn’t want you to kill a certain important NPC important to their plot so they shame you for resorting to combat based abilities in a game where all your character abilities are focussed towards combat. It further crops up when a GM opts to play a system with such a ridicously high power level relative to the implied medieval fantasy world of the setting that the characters are literal demigod like beings above the concerns of everything in the setting so don’t need to care about the petty concerns of mortals because they’re Dr Manhatten wandering around 13th century Europe.. Yes I’m talking about 5E.
A railroad is a situation in a tabletop game where a player doesn’t like the particular lack of freedom in a certain situation so accuses the GM of railroading rather than realising everything inherently has some layer of restriction applied to it because that’s how physics and geography work.
Alternatively railroading is a situation in a tabletop roleplaying game where a GM just can’t be fucked to stretch themselves beyond the narrow series of events they had planned so force their players to comply to that singular vision without any form of deviation.
Fudging dice is for when a GM wants to deny player agency in the most cowardly way possible by not only making it so that the players actions were pointless because the player agreed as part of the social contract to sit down and play a game with a set of rules and if the GM can arbitrarily just change the fundamental nature of those rules as decreed by the dice whenever the situation doesn’t fit their narrow view of what should and shouldn’t happen in any particular situation thus eliminating any point of dice being used in the first place.
And no fudging dice can’t be for the players benefit. There’s no justification. Let their characters die if it comes to that or just rule it that their characters can never die or get instantly resurrected if death is such a problem, which it usually really isn’t. Your players are adults, they wont cry if they lose their fictional character to a bad dice roll. Even if your players are literally children they’ll also be just fine if their character dies most of the time, it’s just a game.
Having fun is a justification used to defend bad systems and poor GMing practices since if 4 other people vaguely had a good time playing in a game then this must mean the game is above all forms of criticism because why would we want to elevate this thing we enjoy to anything beyond something children do for fun?