A feature in any number of more-than-two-player games (be they BoardGame, UnCCG, multiplayer MagicTheGathering, or whatever): where a player who takes an early lead gets thoroughly attacked by the remainder of the players, and that early lead is completely removed.
For example, playing MTG: Congregate early may get you 50 life or more; but that doesn't benefit you much if all you mean is that for the next 12 attack phases, you're the only player who gets attacked. You will often do much better saving it for later, often at instant speed when you or a horde-controlling player is about to die: you may only gain about 20 life, but the difference it makes to your actual chance of winning is likely to be much greater.
Not necessarily a bad thing. See also StopTheLeader.