Her*met"ic*al*ly, adv.
1.
In an hermetical manner; chemically.
Boyle.
2.
By fusion, so as to form an air-tight closure.
⇒ A vessel or tube is hermetically sealed when it is closed completely against the passage of air or other fluid by fusing the extremity; -- sometimes less properly applied to any air-tight closure.
© Webster 1913.