Participants who entered a position at a price extreme — near the high or low of a bar — that immediately reversed against them, leaving them in a losing position. Their urgency to exit creates additional order flow in the direction of the reversal, which amplifies the move and traps further participants from lower-quality entries — a self-reinforcing feedback loop. Trapped buyers are identified by a buying imbalance at a bar's high followed by a bearish close; trapped sellers are the mirror at a bar's low followed by a bullish close.