Source : Webster's Revised Unabridged Dictionary (1913)

Hermetic \Her*met"ic\, Hermetical \Her*met"ic*al\, a. [F.
   herm['e]tique. See Note under {Hermes}, 1.]
   1. Of, pertaining to, or taught by, Hermes Trismegistus; as,
      hermetic philosophy. Hence: Alchemical; chemic.
      ``Delusions of the hermetic art.'' --Burke.

            The alchemists, as the people were called who tried
            to make gold, considered themselves followers of
            Hermes, and often called themselves Hermetic
            philosophers.                         --A. B.
                                                  Buckley.

   2. Of or pertaining to the system which explains the causes
      of diseases and the operations of medicine on the
      principles of the hermetic philosophy, and which made much
      use, as a remedy, of an alkali and an acid; as, hermetic
      medicine.

   3. Made perfectly close or air-tight by fusion, so that no
      gas or spirit can enter or escape; as, an hermetic seal.
      See Note under {Hermetically}.

   {Hermetic art}, alchemy.

   {Hermetic books}.
      (a) Books of the Egyptians, which treat of astrology.
      (b) Books which treat of universal principles, of the
          nature and orders of celestial beings, of medicine,
          and other topics.

Source : WordNet®

hermetic
     adj : completely sealed; completely airtight