Most nuclear refers to something or someone that possesses the highest level of radioactivity, power or explosiveness. Antonyms for most nuclear are words that express the opposite meaning, such as harmless, safe or inert. Harmless describes something or someone that is unlikely to cause harm or injury, while safe refers to being free from danger or risk. Inert, on the other hand, pertains to something or someone that lacks physical or chemical activity, and therefore is unable to cause any impact. These antonyms can be used to describe things that are not radioactive or weapons, such as foods or materials that are safe for human consumption, or substances that are not explosive.