adulterate

Definition

To mix or add something unhealthy, unpleasant, or degrading to something good, especially so that it becomes unsatisfactory or unpleasant in quality or effect, in character, or in spirit.

한국어 좋은 것을 나쁘게 만들거나 오염시키는 것

Example

"She refused to eat the store's adulterated milk, which was found to be past its fresh shelf life."