DOF means degrees Of Freedom
DOF (or level of freedom) is a term you encounter at VR, and then it mainly concerns the two terms 3DOF and 6DOF. Both indicate how much freedom of movement you have: with 3DOF it is about moving forward, backwards and up/down. At 6DOF come there: deviation, height and roles. The developments in the field of sensors and controllers are going very quickly so 6DOF will become more common. Incidentally, you'll also find terms like 3DOF and 6DOF in normal (non-VR) games. Https://www.youtube.com/watch?v=BJhkKdlxpgo