Noclip mode, also known as Noclipping mode or simply Noclipping, is a modification to the behavior of a game's engine, usually a first person shooter or other 3d game set in first person.
Clipping in this case refers to the 3d engine's collision detection, rather than the calculation over the displaying of the polygon.
When enabled, it allows the user to walk through walls, and depending on the game, may automatically enable flight and invincibility.
Noclipping is nearly always a cheat, usually a left over relic from the debugger's toolbox.
While the first game set in the first person to allow users to noclip was Doom with the cheat code of idspispopd, the mode's name originally comes from Quake, where the console command idnoclip enabled and disabled it.
If you don't know if a specific game has a noclip mode available, look it up, the sheer mass makes a complete list unfeasible.
How to enable noclip mode for fun and profit:
If you are a character in a land of Sword and Sorcery, spells may be available. Alternately, locate an appropriate artifact or Loophole. Results and costs may vary, and misuse may cause Dungeon collapse
If you locate technology allowing you to walk through walls, the gods will take a sacrifice in payment if you use it for evil. The favored way is to cause the device to fail when a member of your team is still in the wall.
Due to he nature of atoms, there is a very, very small chance you could simply avoid every atom in the wall, feel free to try. The management is not responsible for damage caused.