mikroorganisme yang hidup dan tumbuh dalam keadaan tidak ada atau hampir tidak ada molekul oksigen.

Merriam-Webster Online Dictionary
anaerobe (noun)
an organism - anaerobic
anaerobe (Wikipedia)
Spinoloricus nov. sp., a metazoan that metabolises with hydrogen, lacking mitochondria and instead using hydrogenosomes.

An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It may react negatively or even die if oxygen is present. (In contrast, an aerobic organism (aerobe) is an organism that can survive and grow in an oxygenated environment.)

An anaerobic organism may be unicellular (e.g. protozoans,bacteria) or multicellular. For practical purposes, there are three categories of anaerobe: obligate anaerobes, which are harmed by the presence of oxygen; aerotolerant organisms, which cannot use oxygen for growth but tolerate its presence; and facultative anaerobes, which can grow without oxygen but use oxygen if it is present.