Unwinnable

A player’s hand is impossible to complete if the remaining tile(s) the player needs to achieve their hand are not possible to obtain either due to the required tile(s) already being discarded (dead tiles) or are used in another player’s exposure

If a player’s hand becomes unwinnable a dead hand challenge may be declared by another player.

Example: Player A has four exposures and only a Pair of 6 Dot will complete their hand for Mah Jongg. During Player B’s turn, Player B exposes a Pung of 6 Dots. Player A now has an unwinnable hand since Player A needs a Pair of 6 Dot however this pair is impossible to achieve since three of the four 6 Dot tiles have been used in Player B’s exposure and a Pair can not be created with a Joker tile.