Glossary Entry: Collision Detection

Collision detection refers to the portion of a game's code that determines if two (or more) objects are touching. It's generally responsible for ensuring that objects don't pass through each other, that objects stop falling when they land on something, and that projectiles properly react to striking something.

If a game features a noclip cheat code, a player can enable or disable the collision detection code for their in game character. While disabled, they can walk through walls and do other weird stuff that the collision detection usually prevents.