An enclosure is something that closes you in, like a pen or a cage. When a cobra disappeared from an enclosure at the Bronx Zoo, the entire Reptile House had to be shut down until the snake was found.

An enclosure can also be something that's included in an envelope with a cover letter of some sort. If you're sending a letter to your literary agent and you’re including a few pages of your latest limericks, you might put "enc." at the bottom of the letter, to indicate that you've included something extra in the envelope — an enclosure.

Definitions of enclosure
  1. noun
    a structure consisting of an area that has been enclosed for some purpose
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    Holy Sepulcher
    the sepulcher in which Christ's body lay between burial and resurrection
    a commercial aquarium featuring trained dolphins
    Mausoleum at Halicarnasus
    a white marble mausoleum 140 feet high built in 352 BC at Halicarnassus as a memorial to a king; destroyed in 1402
    Taj Mahal
    beautiful mausoleum at Agra built by the Mogul emperor Shah Jahan (completed in 1649) in memory of his favorite wife
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    cage, coop
    an enclosure made or wire or metal bars in which birds or animals can be kept
    cargo area, cargo deck, cargo hold, hold, storage area
    the space in a ship or aircraft for storing cargo
    an enclosure or receptacle for odds and ends
    a natural or artificial enclosed space
    an enclosure of residences and other building (especially in the Orient)
    an enclosure in a court of law where the defendant sits during the trial
    echo chamber
    an enclosed space for producing reverberation of a sound
    lock, lock chamber
    enclosure consisting of a section of canal that can be closed to control the water level; used to raise or lower vessels that pass through it
    a streamlined enclosure for an aircraft engine
    an enclosure for confining livestock
    an enclosure in which animals are made to fight
    pen, playpen
    a portable enclosure in which babies may be left to play
    an enclosed space in which the air pressure is higher than outside
    dog pound, pound
    a public enclosure for stray or unlicensed dogs
    niche, recess
    an enclosure that is set back or indented
    an indoor enclosure for keeping and raising living animals and plants and observing them under natural conditions
    an enclosure for animals (as chicken or livestock)
    air lock, airlock
    a chamber that provides access to space where air is under pressure
    alcove, bay
    a small recess opening off a larger room
    apse, apsis
    a domed or vaulted recess or projection on a building especially the east end of a church; usually contains the altar
    aquarium, fish tank, marine museum
    a tank or pool or bowl filled with water for keeping live fish and underwater animals
    a yard adjoining a barn
    a cage in which a bird can be kept
    air-raid shelter, bomb shelter, bombproof
    a chamber (often underground) reinforced against bombing and provided with food and living facilities; used during air raids
    burial chamber, sepulcher, sepulchre, sepulture
    a chamber that is used as a grave
    caisson, cofferdam, pneumatic caisson
    large watertight chamber used for construction under water
    camera obscura
    a darkened enclosure in which images of outside objects are projected through a small aperture or lens onto a facing surface
    chicken run, chicken yard, fowl run, hen yard
    an enclosed yard for keeping poultry
    a pit for cockfights
    cinerarium, columbarium
    a niche for a funeral urn containing the ashes of the cremated dead
    the chamber of a nuclear reactor containing the fissile material where the reaction takes place
    cattle pen, corral, cow pen
    a pen for cattle
    a pen that is fenced so that young animals can enter but adults cannot
    cylinder, piston chamber
    a chamber within which piston moves
    an area adjacent to farm buildings
    fireplace, hearth, open fireplace
    an open recess in a wall at the base of a chimney where a fire can be built
    firing chamber, gun chamber
    chamber that is the part of a gun that receives the charge
    fold, sheep pen, sheepcote, sheepfold
    a pen for sheep
    an enclosed chamber in which heat is produced to heat buildings, destroy refuse, smelt or refine ores, etc.
    holding paddock, holding pen, holding yard
    a pen where livestock is temporarily confined
    a cage (usually made of wood and wire mesh) for small animals
    hyperbaric chamber
    a large chamber in which the oxygen pressure is above normal for the atmosphere; used in treating breathing disorders or carbon monoxide poisoning
    a pen for livestock in southern Africa
    (Islam) a niche in the wall of a mosque that indicates the direction of Mecca
    pen where racehorses are saddled and paraded before a race
    particle detector
    a chamber in which particles can be made visible
    a pen where stray animals are confined
    cavity resonator, resonating chamber, resonator
    a hollow chamber whose dimensions allow the resonant oscillation of electromagnetic or acoustic waves
    an enclosure for cattle that have been rounded up
    squirrel cage
    cage with a cylindrical framework that rotates as a small animal runs inside it
    steam chest
    the chamber from which steam is distributed to a cylinder
    enclosed yard where cattle, pigs, horses, or sheep are kept temporarily
    fireroom, stokehold, stokehole
    (nautical) chamber or compartment in which the furnaces of a ship are stoked or fired
    packing box, stuffing box
    a small chamber in which packing is compressed around a reciprocating shaft or piston to form a seal
    pigpen, pigsty, sty
    a pen for swine
    a vivarium in which selected living plants are kept and observed
    a doughnut-shaped chamber used in fusion research; a plasma is heated and confined in a magnetic bottle
    vacuum chamber
    a chamber from which nearly all matter (especially air) has been removed
    type of:
    a part of a structure having some specific characteristic or function
  2. noun
    a naturally enclosed space
    synonyms: natural enclosure
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    any large dark enclosed space
    an enclosure within which something originates or develops (from the Latin for womb)
    type of:
    an empty area (usually bounded in some way between things)
  3. noun
    the act of enclosing something inside something else
    synonyms: enclosing, envelopment, inclosure
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    boxing, packing
    the enclosure of something in a package or box
    encasement, incasement
    the act of enclosing something in a case
    the act of binding something into a bundle
    type of:
    insertion, introduction, intromission
    the act of putting one thing into another
  4. noun
    something (usually a supporting document) that is enclosed in an envelope with a covering letter
    synonyms: inclosure
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    type of:
    document, papers, written document
    writing that provides information (especially information of an official nature)
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