The crossword solution for the term 'VACUUM's Lack' is AIR, which is a three-letter word. AIR is a mixture of gases that make up the Earth's atmosphere, and it is composed of nitrogen, oxygen, argon, and other trace gases. AIR is essential for life on Earth, as it provides oxygen for respiration and helps to regulate the temperature of the planet. Vacuums lack AIR because they are designed to suck up dust and debris from surfaces, leaving a VACUUM behind.