The term 'GAS IN GLOWING SIGNS' can be summarized by the word 'NEON', which is a four-letter word. NEON is a type of gas that is used in glowing signs, such as NEON signs. It is a noble gas that is colorless, odorless, and non-flammable. When an electric current is passed through it, it emits a bright light. NEON is used in many different types of signs, including advertising signs, decorative signs, and safety signs.