Dictionary.net

To transform, as the venous blood, into arterial blood by exposure to oxygen in the lungs; to make arterial.

To transform, as the venous blood, into arterial blood by exposure to oxygen in the lungs; to make arterial.

To transform dark red venous into bright red arterial blood during its passage through the lungs, gills, or any respiratory apparatus. This transformation consists in the removal of carbon dioxid from the blood and the addition of oxygen.