1. Relating to being mixed with foreign material: An impure mixture of water and salt can be separated by distillation, with water as the distillate and salt as the solid residue; however, no matter what method is used, it is usually impossible to separate all of the impure elements completely from a substance.
2. A reference to being dirty: Parasites thrive and multiply in impure water.
3. Morally wrong; especially having immoral behavior or thoughts: The cartoonists of the drawings were suspected of harboring impure contents in their illustrations.
4. Etymology: from Latin impurus; from in-, "not" + purus, "pure".