"Not pure" can refer to any number of things, from questionable motives to impure substances. In each case, there are a variety of synonyms that can be used to describe these things more precisely. For instance, the term "adulterated" can be used to refer to a substance that has been mixed with other substances, thereby making it impure. Similarly, "corrupt" is often used to describe people or organizations that engage in unethical or dishonest behavior. Other possible synonyms for "not pure" include "polluted," "tainted," "contaminated," "debased," and "defiled." By using these more precise terms, we can communicate more effectively and accurately about the things that are not pure in our world.