seal

noun
  1. A device or substance used to join two things together so as to prevent them from coming apart or to prevent anything from passing between them. noun
    The envelope was closed with a wax seal.
    Make sure the lid is on tight to ensure a good seal.
  2. An official mark or stamp on a document, used to show that it is genuine or has been approved officially. noun
    The document bore the royal seal.
    The notary placed his seal on the contract.
  3. A marine mammal that is related to the sea lion and walrus, typically living in cold regions. noun
    We saw a seal basking on the rocks by the shore.
    Seals are known for their playful nature.
  4. To close or fasten something securely or completely. verb
    She sealed the box with tape.
    He sealed the deal with a handshake.
  5. To make something definite or irrevocable. verb
    The victory sealed their place in the finals.
    Her fate was sealed when she signed the contract.