The title of the short story "The Most Dangerous Game" carried two meanings. First, it is referring to "game" as in hunting game, or the animals being hunted. We see this meaning connected to the story in the conversation between Whitney and Rainsford, and later between Rainsford and Zaroff. Whitney sympathizes with the prey early on, whereas Rainsford doesn't care what the prey feels. In an ironic twist, he learns from Zaroff that men are his prey. They are the most dangerous game for hunting because they can think and reason, unlike even the most intuitive animals.
The second meaning is "game" as in something that you play. Zaroff refers to hunting men as a "game." It has rules, a clear winner, and a reward. This game is dangerous, however, because it crosses moral and ethical lines by treating fellow human beings as any other animal. It is dangerous because it causes the participants to choose to kill someone in order to avoid death themselves. This perception of human beings is very dangerous.