An organ found in air-breathing vertebrate animals which functions in air respiration. It transfers atmospheric oxygen from the air to the blood, and carbon dioxide and other waste gases from the blood to the air.
Most animals have a pair; one species of lungfish has just one, and other primitive fish may have lunglike air bladders (the swim bladder, found in many bony fishes, evolved from the lung).
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.