What is the meaning of the word "seal"?

Definitions:

a stamp affixed to a document (as to attest to its authenticity or to seal it) noun
- the warrant bore the sheriff's seal
affix a seal to verb
- seal the letter
close with or as if with a seal verb
- We sealed the invitations with hot wax.
decide irrevocably verb
- sealing dooms
fastener consisting of a resinous composition that is plastic when warm noun
- used for sealing documents and parcels and letters
the pelt or fur (especially the underfur) of a seal noun
- a coat of seal