(BOD) 1. the amount of dissolved oxygen removed from water by aquatic microorganisms in the process of biological decomposition of organic matter —note BOD₅ is a standard value, measured in mg/l, indicating the amount of oxygen utilized by microorganisms in a five-day period when incubated at a temperature of 20°C (68°F) 2. the amount of molecular oxygen required to stabilize decomposable matter by aerobic biochemical action —synonym biological oxygen demand This definition last updated 10/24/2008