1. adj. [Geology]
The condition of an environment in which free oxygen is lacking or absent.
Synonyms: anoxic
2. adj. [Geology]
A description of organisms that can survive in the absence of oxygen, particularly bacteria.
3. adj. [Drilling Fluids]
Pertaining to systems, reactions or life processes of species, such as bacteria, in which atmospheric oxygen is not present or not required for survival.
Antonyms: aerobic