Something you say when an already-immersive video game (such as Fallout 4 or Skyrim) becomes even more immersive as a result of a user-created modification. In order for a user-created modification to be considered immersive as fuck, they have to be lore friendly, somewhat realistic, and/or balanced (AKA not op).
Viewer: But is it immersive as fuck?
MXR: Well, the weapon is only obtainable after you complete a ridiculously hard quest. Not only that, but the ammunition for this weapon costs a fortune. This means that this mod is indeed immersive as fuck!
The act of using noise cancelling headphones to watch pornography while masturbating in order to feel more involved. This can also be levelled up by adding a VR headset.
I had a cheeky immersive wank earlier, it really felt like Cindy was moaning right in front of me; I came so much quicker!
The way stupid Army Officers interact with digitized "foreign partners" through avatars in a huge, gay, and expensive computer based environment that is routinely broken and relies on stereotypes to teach soldiers about the world as a petting zoo.
"Usin' thus here high tech 'puterized deeevice ar soldiers kin act immersively with them ferin pagan bastards that weez here to save."