Fly poison typically refers to a substance that is used to eliminate flies and other insects. However, there are other words that can be used in place of "fly poison". For example, "insecticide" is a broad term for a substance that is used to kill insects. "Pesticide" is another similar word that can be used in place of "fly poison". "Fly repellent" is a term used to describe a substance that keeps flies away rather than killing them. Other words that are synonymous with "fly poison" include "bug spray", "bug killer", and "insect repellent". Regardless of which term you use, it is important to use such substances safely and responsibly.