What is strong party discipline

Case it refers to administrative sanctions such as fines or expulsion that the Communist Party can impose on its members for actions such as corruption or disagreeing with the party.

Strong party discipline simply refers to administrative discipline, for example, fines or removals that the Communist Party can force on its members for actions like corruption or even something as simple as disagreeing with the other members of the party. If they don't vote the party line, they can even risk losing their seat.