This acronym stands for:
Previews Of Coming Attractors.
This is a very quiet and insidious form of attractor! Before the session starts, a fleeting thought occurs about what the target might be. If not set aside (See the term, S.A.), this becomes a S.C.W.E.R.L. and can turn an RV session into a nightmare
You will also see this referred to as "Advanced Visuals", even though it is not always visual in nature.