The term ALVEOLI SITE refers to the microscopic air SACS in the lungs. These SACS, known as alveoli, are where oxygen and carbon dioxide are exchanged between the lungs and the bloodstream. The four letter solutions for this term are LUNG, SACS, EBAY, and ARENA. LUNG is the organ in which the alveoli are located, SACS refers to the alveoli themselves, EBAY is an acronym for the exchange of gases between the alveoli and the bloodstream, and ARENA is a term used to describe the shape of the alveoli.