"Air-built" is a term that describes structures that are light and airy in their construction. Some synonyms for this term include ethereal, lightweight, delicate, graceful, and flowing. These words conjure up images of structures that are almost weightless and seem to float in the air. They suggest a sensation of movement or fluidity in the way the structure is built. Other synonyms include insubstantial, flimsy, and fragile, which suggest a certain amount of vulnerability or instability in the structure. Together, these synonyms help to capture the poetic and ephemeral nature of air-built structures, which are often admired for their beauty and simplicity.