mephitis

(noun) a poisonous or foul smelling gas emitted from the earth.

(noun) a distinctive odor that is offensively unpleasant. Synonyms: malodor, malodour, stench, stink, reek, fetor, foetor.

(noun) in some classifications: type genus of the subfamily Mephitinae. Synonyms: Mephitis, genus Mephitis.