a problem arising in the case of public goods because those who do not contribute to the costs of providing the public good cannot be excluded from the benefits of the good.
the problem that occurs when someone thinks he may be able to enjoy something without paying for it, and so fails to contribute to the cost; free-rider problems arise in the provision of public goods
The problem, arising in the context of public goods, that no individual is willing to contribute towards the cost of something when she hopes that someone else will bear the cost instead.