seal¹ / sēl/ • n. 1. a device or substance that is used to join two things together so as to prevent them from coming apart or to prevent anything from passing between them: blue smoke from the exhaust suggests worn valve seals. ∎  [in sing.] the state or fact of being joined or rendered impervious by such a substance or device: many fittings have tapered threads for a better seal. ∎  the water standing in the trap of a drain to prevent sewer gas from backing up through the drain, considered in terms of its depth. 2. a piece of wax, lead, or other material with an individual design stamped into it, attached to a document to show that it has come from the person who claims to have issued it. ∎  a design embossed in paper for this purpose. ∎  an engraved device used for stamping a design that authenticates a document. ∎ fig. a thing regarded as a confirmation or guarantee of something: the International Monetary Fund is likely to give a seal of approval to the Mexican plan. ∎  a decorative adhesive stamp. ∎  (the seal) (also the seal of confession or the seal of the confessional) the obligation on a priest not to divulge anything said during confession: I was told under the seal.• v. [tr.] fasten or close securely: he folded it, sealed the envelope, and walked to the mailbox. ∎  (seal something in) prevent something from escaping by closing a container or opening. ∎  (seal something off) isolate an area by preventing or monitoring entrance to and exit from it: anti-terrorist squad officers sealed off the area to search for possible bombs. ∎  apply a nonporous coating to (a surface) to make it impervious: seal the finish with a satin varnish. ∎  fry (food) briefly in hot fat to prevent it from losing too much of its moisture during subsequent cooking: heat the oil and seal the lamb on both sides. ∎  fix a piece of wax or lead stamped with a design to (a document) to authenticate it. ∎  conclude, establish, or secure (something) definitively, excluding the possibility of reversal or loss: to seal the deal he offered Thornton a place on the board of the nascent company. ∎  (in the Mormon church) mark (a marriage or adoption) as eternally binding in a formal ceremony.PHRASES: my (or his, etc.) lips are sealed used to convey that one will not discuss or reveal something.put (or set) the seal on give the final authorization to: the UN envoy hopes to set the seal on a lasting peace. ∎  provide or constitute the final confirmatory or conclusive factor: the rain set the seal on his depression.seal someone's fatesee fate.set (or put) one's seal to (or on) mark with one's distinctive character: it was the Stewart dynasty which most markedly set its seal on the place.under seal under legal protection of secrecy: the judge ordered that the videotape be kept under seal.DERIVATIVES: seal·a·ble adj.seal² • n. a fish-eating aquatic mammal with a streamlined body and feet developed as flippers, returning to land to breed or rest. Two families: Phocidae (the true seals) and Otariidae (the eared seals, including the fur seals and sea lions). ∎ another term for sealskin.• v. [intr.] [usu. as n.] (sealing) hunt for seals.

seal2 a piece of wax, lead, or other material with an individual design stamped into it, attached to a document to show that it has come from the person who claims to have issued it. Recorded from Middle English, the word comes via Old French from Latin sigillum ‘small picture’, diminutive of signum ‘a sign’.
seals of office in the UK, are engraved seals held during tenure of an official position, especially that of Lord Chancellor or Secretary of State, and symbolizing the office held.
seal of the confessional in the Catholic Church, the obligation on a priest not to disclose any part of a person's confession.