Anaerobically is an adverb that describes a process taking place without the presence of oxygen. There are a few synonyms to use in place of anaerobically in writing or speech. The first synonym is "hypoxically," which refers to a condition of low oxygen levels. Another synonym for anaerobically is "anoxically," which describes a complete lack of oxygen in a given environment. Additionally, one could use the word "aerobically challenged" to convey the same meaning as anaerobically. Each of these synonyms provides alternative language choices for those seeking to communicate the absence of oxygen in a particular context.