1.
If you ~ a substance, for example food or drink, you add water to it to make it weaker.
You can ~ a glass of wine and make it last twice as long...
I bought a water-based paint, then decided to water it down even more.
= dilute
PHRASAL VERB: V P n (not pron), V n P
2.
If something such as a proposal, speech, or statement is watered down, it is made much weaker and less forceful, or less likely to make people angry.
Proposed legislation affecting bird-keepers has been watered down.
= tone down
VERB: be V-ed P
see also watered-down