There are terms used to imply that a GM/DM is not playing on the up and up with players.
One of those terms is "fudging" specifically related to dice usage. This gets called when a GM rolls a dice but either rolls again till he/she gets a desired result or dismisses the result in preference of another result.
Another term used is "railroading. This gets called when players think the GM/DM is forcing them down a course of action that the players might otherwise not have chosen.
First of all, I'd like to address "fudging the dice". For any player that likes to lawyer up, the bad news is, GM's can "fudge" all day long and it is not cheating. Everything about the game in terms of adjudicating results and actions is within the GM/DM's discretion.
There are times, in the course of a game session, the GM will need to keep the players from trying to out think them and anticipate what else might be going on or coming up. Using fake rolls or choosing to ignore dice results for something the GM has in mind is perfectly within the means in the interest of the game.
Now, if the DM/GM is playing favorites among players or PC's by "fudging" dice rolls and there is proof of it, that is not a trait players want to see in a GM. Good DM's don't play favorites.
In regards to "Railroading". While I personally think it's in the best interests of a good game to keep options open for players throughout the game, there are some things that are less or even not negotiable. It really wouldn't be a game if the one choice or direction wasn't made, ergo, the GM points and says "Go that way!" and it's all good.
Remember, killing things, capturing them, rescuing, exploring and other action things are in the realm of the player. Putting everything in it's place to be found, fought, captured, rescued and explored is the realm of the GM/DM. If they didn't get you to the place where the adventure is, it would be one heck of a boring game for the players. You have to give the DM some room to get you where you need to be.