Unbreathable is a term used to describe air that is devoid of oxygen or contains dangerous pollutants. This word is often used in reference to environments or conditions that are hazardous to human health. Some synonyms for unbreathable include suffocating, stifling, oppressive, noxious, toxic, and unhealthy. These words give a sense of the discomfort and danger that arises from air that is not suitable for human respiration. Other synonyms include asphyxiating, smoggy, and contaminated, which further emphasize the severity of inhaling such air. In situations where the air quality is unbreathable, individuals should take immediate steps to protect themselves and avoid exposure.