said of a seal: airtight
impervious to external influences
(often Hermetic) of or relating to the Gnostic and alchemical writings attributed to Hermes Trismegistus
(often Hermetic) abstruse or recondite
hermetically adv
hermeticism noun
[via Latin from Hermes Trismegistus (from Greek Hermēs trismegistos, literally ‘Hermes thrice-greatest’), legendary author of mystical and alchemical works; (sense 1) from the belief that Hermes Trismegistus invented a magic seal to keep vessels airtight]