Definition of seal noun from the Oxford Advanced American Dictionary

     

    seal

     noun
    noun
    NAmE//sil//
     
     
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    sea animal
  1. 1 [countable] a sea animal that eats fish and lives around coasts. There are many types of seals, some of which are hunted for their fur a colony of seals harbor seals basking on the rocks The annual seal hunt takes place on the pack ice off Greenland.
  2. official mark
  3. 2[countable] an official design or mark, stamped on a document to show that it is genuine and carries the authority of a particular person or organization The letter bore the president's seal.
  4. making something definite
  5. 3[singular] a thing that makes something definite The project has been given the government's seal of approval (= official approval). I looked upon the gift as a seal on our friendship.
  6. on containers
  7. 4[countable] a substance, strip of material, etc. used to fill a crack so that air, liquid, etc. cannot get in or out a jar with a rubber seal in the lid Only drink bottled water and check the seal isn't broken.
  8. on letters/boxes
  9. 5[countable] a piece of wax (= a soft substance produced by bees ), soft metal, or paper that is placed across the opening of something such as a letter or box and that has to be broken before the letter or box can be opened He broke the wax seal and unrolled the paper.
  10. 6a piece of metal, a ring, etc. with a design on it, used for stamping a wax or metal seal
  11. Idioms
    set the seal on something(formal)
     
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    to make something definite or complete Her election to the premiership set the seal on a remarkable political career.
    under seal(formal)
     
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    (of a document) in a sealed envelope that cannot be opened before a particular time
See the Oxford Advanced Learner's Dictionary entry: seal