When something is described as "not natural", it means that it goes against the laws of nature or does not occur naturally. There are several synonyms for this phrase, including "artificial", "unnatural", "man-made", "synthetic", "inorganic", and "manufactured". These words describe anything that is created or manipulated by humans, and may not exist without human intervention. Examples of things that are not natural include plastic, genetically modified organisms, and processed foods. While these items may be convenient and useful, they are not considered natural because they are not found in nature and do not occur without human intervention.