Something that's pure, not mixed with other ingredients, is unadulterated. If you stand in your yard every time it rains singing "Singin' in the Rain" with unadulterated enthusiasm, your neighbors will eventually call the police.
Food or drink that is pure is also said to be unadulterated. Some people like chocolate milk, but you might prefer the unadulterated variety. The adjective unadulterated also means "without qualifications," and it can be used in a negative way to mean "complete and utter." You'd probably feel like an unadulterated idiot if you shocked yourself by sticking a knife in the toaster after being advised not to.