The term 'noxious gas' can be summarized by the 6-letter word 'MIASMA'. MIASMA is a term used to describe a noxious, poisonous, or foul-smelling vapor or mist that is often created by decaying organic matter. It is also used to describe a heavy, oppressive atmosphere or feeling of gloom. Noxious gases are often released into the environment as a result of human activities such as burning fossil fuels and industrial processes.