A trapped trader occurs when a large number of market orders occur at a top or bottom. It is very similar to when ZoneTraderPro identifies absorption, however it is a different algorithm which is looking at more than just one price level, which is why you do not see it at every POC signal.

Trapped traders are important because those people are wrong and they will have to cover when they get stopped out. This creates additional demand in the direction that ZoneTraderPro users are in.