The term 'as impalpable or intangible as air' can be summarized by two crossword solutions: ETHEREAL (8 letters) and AURA (4 letters). ETHEREAL is an adjective that means extremely delicate and light in a way that seems too perfect for this world. It is often used to describe something that is spiritual or heavenly. AURA, on the other hand, is a noun that refers to a distinctive atmosphere or quality that surrounds a person or thing. It is often associated with a sense of mystery or power. Together, these two words capture the idea of something being as impalpable or intangible as air.