seal

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various aquatic carnivorous mammals of the families Phocidae and Otariidae, found chiefly in cold regions and having a sleek torpedo-shaped body and limbs that are modified into paddlelike flippers.
• noun The pelt or fur of one of these animals, especially a fur seal.
• noun Leather made from the hide of one of these animals.
• intransitive verb To hunt seals.
• noun A device or material that is used to close off or fasten an opening or connection, especially to prevent the escape of a liquid or gas.
• noun An airtight closure.
• noun Something, such as a piece of tape, that is placed on a product or package to show that the contents have not been tampered with.
• noun The water in the trap of a drain that prevents sewer gas from escaping into a room.
• noun A design used to identify a person or thing or to show that something is authentic, accurate, or of good quality.
• noun A small decorative paper sticker.
• noun A die or signet having a raised or incised emblem used to stamp an impression on a receptive substance such as wax or lead.
• noun The impression so made.
• noun The design or emblem itself, belonging exclusively to the user.
• noun A small disk or wafer of wax, lead, or paper bearing such an imprint and affixed to a document to prove authenticity or to secure it.
• noun An indication or symbol regarded as guaranteeing or authenticating something.
• transitive verb To close or fasten with a seal.
• transitive verb To prevent (a liquid or gas) from escaping.
• transitive verb To cover, secure, or fill up (an opening).
• transitive verb To apply a waterproof coating to.
• transitive verb To secure or prevent passage into and out of (an area). Often used with off:
• transitive verb To affix a seal to (something) in order to prove authenticity, accuracy, or quality.
• transitive verb To establish or determine irrevocably.
• transitive verb Mormon Church To make (a marriage, for example) eternally binding; solemnize forever.
• idiom ((one's) lips are sealed) Used to indicate that one will not disclose a piece of information.
• idiom (under seal) Having an impression or emblem attesting to a document's authenticity and reliability.

from The Century Dictionary.

• noun A marine car nivorous mammal of the order Feræ, suborder Pinnipedia, and family Phocidæ or Otariidæ; any pinniped not a walrus—for example, a hair-seal, a fur-seal, an eared seal, of which there are numerous genera and species.
• noun In heraldry, a bearing representing a creature something like a walrus, with a long fish-like body and the head of a carnivorous animal.
• To hunt or catch seals.
• noun Sealskin; leather made from the skin of the seal.
• noun The amount of lap over the edge of an opening by which a lid or valve projects to make a tight joint and prevent leakage past it.
• noun See day.
• noun An impressed device, as of a letter, cipher, or figure, in lead, wax, paper, or other soft substance, affixed to a document in connection with or in place of a signature, as a mark of authenticity and confirmation, or for the purpose of fastening up the document in order to conceal the contents.
• noun The engraved stone, glass, or metal stamp by which such an impression is made. Seals are sometimes worn as rings, and frequently as pendants from the watch-chain or fob.
• noun A small disk of paper, or the like, attached to a document after the signature, and held to represent the seal of wax, which is in this case dispensed with.
• noun That which authenticates, confirms, or ratifies; confirmation; as surance; pledge.
• noun A sealed instrument; a writ or warrant given under seal.
• noun The office of the sealer or official who authenticates by affixing a seal.
• noun The wax or wafer with which a folded letter or an envelop is closed; also, any other substance similarly used to assure security or secrecy, as lead for sealing bonded cars, etc. See leaden seal, below.
• noun Figuratively, that which effectually closes, confines, or secures; that which makes fast.
• noun In plumbing, a small quantity of water left standing in a trap or curve of tubing connected with a drain or sewer in order to prevent the escape of gas from below.
• noun Eccles.:
• noun The sign of the cross.
• noun Baptism.
• noun Confirmation.
• noun Same as holy lamb (which see, under lamb).
• noun In old medicine, the so-called sigil or signature of a plant, mineral, etc. See signature.