Source : Webster's Revised Unabridged Dictionary (1913)

Mephitic \Me*phit"ic\, Mephitical \Me*phit"ic*al\, a. [L.
   mephiticus, fr. mephitis mephitis: cf. F. m['e]phitique.]
   1. Tending to destroy life; poisonous; noxious; as, mephitic
      exhalations; mephitic regions.

   2. Offensive to the smell; as, mephitic odors.

   {Mephitic air} (Chem.), carbon dioxide; -- so called because
      of its deadly suffocating power. See {Carbonic acid},
      under {Carbonic}.

Source : WordNet®

mephitic
     adj : of noxious stench from atmospheric pollution [syn: {miasmic}]