1) ADJ: ADJ n If a container has a hermetic seal, the seal is very tight so that no air can get in or out. [TECHNICAL]

This would permit air to enter, breaking the hermetic seal of the jar.

Derived words:
hermetically [[t]hɜː(r)me̱tɪkli[/t]] ADV ADV -ed, ADV after v

The batteries are designed to be leak-proof and hermetically sealed.

2) ADJ-GRADED (disapproval) You use hermetic to describe something which you disapprove of because it seems to be totally separate from other people and things in society. [WRITTEN]

Its film industry operates in its own curiously hermetic way...

Their work is more cosily hermetic than ever.

English dictionary. 2008.