Adjective
Of, pertaining to, or taught by, Hermes Trismegistus; as, hermetic philosophy. Hence: Alchemical; chemic.
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.
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.
Source: Webster's dictionary