1. Completely sealed, especially against the escape or entry of air.
2. Impervious to outside interference or influence: the hermetic confines of an isolated life.
3. often Hermetic
   1. Mythology. Of or relating to Hermes Trismegistus or the works ascribed to him.
   2. Having to do with the occult sciences, especially alchemy; magical.

[New Latin hermēticus, alchemical, from Medieval Latin Hermēs (Trismegistus). See Hermes Trismegistus.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.