The crossword solution for the term 'Fluorescent Bulb Gas' is ARGON, which is a five-letter word. ARGON is a noble gas that is colorless, odorless, and non-flammable. It is the third most abundant gas in the Earth's atmosphere, making up about 0.934% of the air we breathe. ARGON is often used in fluorescent bulbs because it helps to create an environment where the mercury vapor inside the bulb can be excited by electricity, producing visible light.