The phrase "to water down" means to weaken or dilute something, often by adding more of another substance. This can refer to a variety of things such as reducing the strength of an alcoholic drink, making a solution weaker than usual, or toning down the intensity of something. The term is also used figuratively to describe actions that reduce the effectiveness or importance of something, for example when someone says they are "watering down" a policy by including compromises in it.