1. The amount of dissolved oxygen (DO) consumed by micro-organism in the biochemical oxidation of organic and inorganic matter; a commonly used measurement to determine water quality, since the amount of oxygen used is an indicator of the level of organic waste that is present.
2. The standard measurement for determining the level of organic pollution in a sample of water.
3. The oxygen required by aerobic organisms; such as, those in sewage, for metabolism.

It is the amount of oxygen used by micro-organisms feeding on the organic material over a given period. Sewage effluent must be diluted to comply with the statutory BOD before it can be disposed of into "clean" rivers.