1 also seal up
to close an entrance or a container with something that stops air, water etc from coming in or out of it:
The window was sealed shut.
seal a joint/crack/opening/gap
A quick way to seal awkward gaps is to use a foam filler.
Dried milk is kept in hermetically sealed (=very tightly closed) containers.
if a building, area, or country is sealed, no one can enter or leave it:
Authorities plan to seal the border.
to close an envelope, package etc by using something sticky to hold its edges in place:
He wrote the address and sealed the envelope.
to cover the surface of something with something that will protect it:
Wooden decks should be sealed to prevent cracking.
to make something, especially something bad, sure to happen:
The outbreak of war sealed the government's fate.
to make an agreement more formal or definite
to make a victory certain:
Smith's goal sealed the victory.
seal something ↔ inphrasal verb
Fry the meat quickly to seal in the juices.
seal something ↔ offphrasal verb
Following a bomb warning, police have sealed off the whole area.