I believe it means anti-jump scare horror. Aka building up the tension so much that player feels uneasy and start to feel scared even when they see a cockroach roaming around.
The feeling that something may pop up any moment and the mood suggest that, yet nothing is happening. This is mostly used at P.T. as there is only one jump scare (which is something hard to do, as in some playthroughs of PT it never happened) and that is the only way you can die, aka the woman catching you.
But then, I could be wrong. 