D: Any action involving possible benefit or cost, in which the outcome is not yet known.

Every businessman is a gambler. There is always a risk that they will lose money, and a possibility they will make a profit.

Everyone who crosses the road is a gambler. There is a possibility of getting to the other side, and a possibility of being run over.

If you freely choose to take risks, and those around you do not deceive you about those risks, then you are not a victim. If you choose to gamble, knowing that the odds are in the favor of the other party, then you are not a victim (though you are probably stupid).

It is a person's choice to gamble. And losing is their responsibility. This is not to say there are no victims from gambling. Someone's gambling obsession may indirectly hurt children through poverty or neglect. If this is the case, then the person is guilty of child neglect, and forbidding them from gambling is a possible course of action. However this is not a justification for preventing others from gambling. It is immoral to prevent someone from gambling because of the damage that another person may do if they were to do the same thing. There is no moral justification for banning gambling.

Most people will reject the definition of gambling above, but be unable to provide an alternative definition. Usually they will talk a lot about casinos, horse races, and people who have lost their money without actually knowing the difference.

There is an alternative definition

D: Any action involving possible benefit or cost, which has a negative expectation value.
but many people reject the conclusions they are forced to draw from the concept of expectation value, and hence reject the definition in favor of confused rhetoric and slogans.

See