The crossword solution for the term 'Bug Spray Ingredient' is DEET, which is a four-letter acronym. DEET stands for N, N-Diethyl-meta-toluamide, which is a chemical compound used as an active ingredient in insect repellents. It is effective against mosquitoes, ticks, fleas, and other biting insects. DEET has been used since the 1950s and is one of the most widely used insect repellents in the world.