The Collaborative International Dictionary of English v.0.48:

Key \Key\ (k[=e]), n. [OE. keye, key, kay, AS. c[ae]g.]
   1. An instrument by means of which the bolt of a lock is shot
      or drawn; usually, a removable metal instrument fitted to
      the mechanism of a particular lock and operated by turning
      in its place.
      [1913 Webster]

   2. A small device which is inserted into a mechanism and
      turned like a key to fasten, adjust, or wind it; as, a
      watch key; a bed key; the winding key for a clock, etc.
      [1913 Webster]

   3. One of a set of small movable parts on an instrument or
      machine which, by being depressed, serves as the means of
      operating it; the complete set of keys is usually called
      the keyboard; as, the keys of a piano, an organ, an
      accordion, a computer keyboard, or of a typewriter. The
      keys may operate parts of the instrument by a mechanical
      action, as on a piano, or by closing an electrical
      circuit, as on a computer keyboard. See also senses 12 and
      13.
      [1913 Webster +PJC]

   4. A position or condition which affords entrance, control,
      pr possession, etc.; as, the key of a line of defense; the
      key of a country; the key of a political situation. Hence,
      that which serves to unlock, open, discover, or solve
      something unknown or difficult; as, the key to a riddle;
      the key to a problem. Similarly, see also senses 14 and
      15.
      [1913 Webster]

            Those who are accustomed to reason have got the true
            key of books.                         --Locke.
      [1913 Webster]

            Who keeps the keys of all the creeds. --Tennyson.
      [1913 Webster]

   5. That part of a mechanism which serves to lock up, make
      fast, or adjust to position.
      [1913 Webster]

   6. (Arch.)
      (a) A piece of wood used as a wedge.
      (b) The last board of a floor when laid down.
          [1913 Webster]

   7. (Masonry)
      (a) A keystone.
      (b) That part of the plastering which is forced through
          between the laths and holds the rest in place.
          [1913 Webster]

   8. (Mach.)
      (a) A wedge to unite two or more pieces, or adjust their
          relative position; a cotter; a forelock. See Illusts.
          of Cotter, and Gib.
      (b) A bar, pin or wedge, to secure a crank, pulley,
          coupling, etc., upon a shaft, and prevent relative
          turning; sometimes holding by friction alone, but more
          frequently by its resistance to shearing, being
          usually embedded partly in the shaft and partly in the
          crank, pulley, etc.
          [1913 Webster]

   9. (Bot.) An indehiscent, one-seeded fruit furnished with a
      wing, as the fruit of the ash and maple; a samara; --
      called also key fruit.
      [1913 Webster]

   10. (Mus.)
       (a) A family of tones whose regular members are called
           diatonic tones, and named key tone (or tonic) or one
           (or eight), mediant or three, dominant or five,
           subdominant or four, submediant or six, supertonic or
           two, and subtonic or seven. Chromatic tones are
           temporary members of a key, under such names as "
           sharp four," "flat seven," etc. Scales and tunes of
           every variety are made from the tones of a key.
       (b) The fundamental tone of a movement to which its
           modulations are referred, and with which it generally
           begins and ends; keynote.
           [1913 Webster]

                 Both warbling of one song, both in one key.
                                                  --Shak.
           [1913 Webster]

   11. Fig: The general pitch or tone of a sentence or
       utterance.
       [1913 Webster]

             You fall at once into a lower key.   --Cowper.
       [1913 Webster]

   12. (Teleg.) A metallic lever by which the circuit of the
       sending or transmitting part of a station equipment may
       be easily and rapidly opened and closed; as, a telegraph
       key.
       [Webster 1913 Suppl.]

   13. any device for closing or opening an electric circuit,
       especially as part of a keyboard, as that used at a
       computer terminal or teletype terminal.
       [PJC]

   14. A simplified version or analysis which accompanies
       something as a clue to its explanation, a book or table
       containing the solutions to problems, ciphers,
       allegories, or the like; or (Biol.) a table or synopsis
       of conspicuous distinguishing characters of members of a
       taxonomic group.
       [Webster 1913 Suppl.]

   15. (Computers) A word or other combination of symbols which
       serves as an index identifying and pointing to a
       particular record, file, or location which can be
       retrieved and displayed by a computer program; as, a
       database using multi-word keys. When the key is a word,
       it is also called a keyword.
       [PJC]

   Key bed. Same as Key seat.

   Key bolt, a bolt which has a mortise near the end, and is
      secured by a cotter or wedge instead of a nut.

   Key bugle. See Kent bugle.

   Key of a position or Key of a country. (Mil.) See Key,
      4.

   Key seat (Mach.), a bed or groove to receive a key which
      prevents one part from turning on the other.

   Key way, a channel for a key, in the hole of a piece which
      is keyed to a shaft; an internal key seat; -- called also
      key seat.

   Key wrench (Mach.), an adjustable wrench in which the
      movable jaw is made fast by a key.

   Power of the keys (Eccl.), the authority claimed by the
      ministry in some Christian churches to administer the
      discipline of the church, and to grant or withhold its
      privileges; -- so called from the declaration of Christ,
      "I will give unto thee the keys of the kingdom of heaven."
      --Matt. xvi. 19.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

key \key\, a.
   Essential; most important; as, the key fact in the inquiry;
   the president was the key player inthe negotiations.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Key \Key\, v. t. [imp. & p. p. Keved; p. pr. & vb. n.
   Keying.]
   1. To fasten or secure firmly; to fasten or tighten with keys
      or wedges. --Francis.
      [1913 Webster]

   2. (Computers) To enter (text, data) using keys, especially
      those on a keyboard; to keyboard; as, to key the data in
      by hand.
      [PJC]

   3. To adjust so as to be maximally effective in a particular
      situation; -- of actions, plans, or speech; as, to key
      one's campaign speech to each local audience.
      [PJC]

   4. To furnish with a key or keys.
      [PJC]

   To key up.
      (a) (Arch.) To raise (the whole ring of an arch) off its
          centering, by driving in the keystone forcibly.
      (b) (Mus.) To raise the pitch of.
      (c) Hence, (fig.), to produce nervous tension in; as, the
          whole team was keyed up for the championship game.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quay \Quay\, n. [F. quai. See Key quay.]
   A mole, bank, or wharf, formed toward the sea, or at the side
   of a harbor, river, or other navigable water, for convenience
   in loading and unloading vessels. [Written also key.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cotter \Cot"ter\ (k[o^]t"t[~e]r), n.
   1. A piece of wood or metal, commonly wedge-shaped, used for
      fastening together parts of a machine or structure. It is
      driven into an opening through one or all of the parts.

   Note: [See Illust.] In the United States a cotter is commonly
         called a key.
         [1913 Webster]

   2. A toggle.
      [1913 Webster]

WordNet (r) 3.0 (2006):

key
    adj 1: serving as an essential component; "a cardinal rule";
           "the central cause of the problem"; "an example that was
           fundamental to the argument"; "computers are fundamental
           to modern industrial structure" [syn: cardinal,
           central, fundamental, key, primal]
    n 1: metal device shaped in such a way that when it is inserted
         into the appropriate lock the lock's mechanism can be
         rotated
    2: something crucial for explaining; "the key to development is
       economic integration"
    3: pitch of the voice; "he spoke in a low key"
    4: any of 24 major or minor diatonic scales that provide the
       tonal framework for a piece of music [syn: key, tonality]
       [ant: atonalism, atonality]
    5: a kilogram of a narcotic drug; "they were carrying two keys
       of heroin"
    6: a winged often one-seed indehiscent fruit as of the ash or
       elm or maple [syn: samara, key fruit, key]
    7: United States lawyer and poet who wrote a poem after
       witnessing the British attack on Baltimore during the War of
       1812; the poem was later set to music and entitled `The Star-
       Spangled Banner' (1779-1843) [syn: Key, Francis Scott
       Key]
    8: a coral reef off the southern coast of Florida [syn: key,
       cay, Florida key]
    9: (basketball) a space (including the foul line) in front of
       the basket at each end of a basketball court; usually painted
       a different color from the rest of the court; "he hit a jump
       shot from the top of the key"; "he dominates play in the
       paint" [syn: key, paint]
    10: a list of answers to a test; "some students had stolen the
        key to the final exam"
    11: a list of words or phrases that explain symbols or
        abbreviations
    12: a generic term for any device whose possession entitles the
        holder to a means of access; "a safe-deposit box usually
        requires two keys to open it"
    13: mechanical device used to wind another device that is driven
        by a spring (as a clock) [syn: winder, key]
    14: the central building block at the top of an arch or vault
        [syn: keystone, key, headstone]
    15: a lever (as in a keyboard) that actuates a mechanism when
        depressed
    v 1: identify as in botany or biology, for example [syn:
         identify, discover, key, key out, distinguish,
         describe, name]
    2: provide with a key; "We were keyed after the locks were
       changed in the building"
    3: vandalize a car by scratching the sides with a key; "His new
       Mercedes was keyed last night in the parking lot"
    4: regulate the musical pitch of
    5: harmonize with or adjust to; "key one's actions to the
       voters' prevailing attitude"

Moby Thesaurus II by Grady Ward, 1.0:

316 Moby Thesaurus words for "key":
   French pitch, Rasputin, Svengali, TelAutography, Teletype,
   Teletype network, Teletyping, VIP, access, accommodate, accord,
   achromatism, adapt, adjust, adjust to, aerophone, ait,
   amplification, archipelago, assimilate, atoll, attune, axial,
   bad influence, bang, bar, barricade, batten, batten down, bell,
   big wheel, bilingual text, bolt, bottle opener, button, button up,
   can opener, cast, catchword, cay, centermost, central, centralized,
   centric, centroidal, centrosymmetric, choke, choke off, chromatism,
   chromism, church key, clap, clarification, classical pitch, clavis,
   close, close up, closed-circuit telegraphy, clue, code, color,
   color balance, color harmony, color scheme, coloration, coloring,
   complexion, concentrated, constrict, contain, continental island,
   contract, coordinate, coral head, coral island, coral reef,
   corkscrew, court, cover, crib, critical, crucial, cue, cue word,
   cut to, decipherment, decoding, decorator color, depth,
   description, dominant, double reed, duplex telegraphy, electricity,
   embouchure, eminence grise, equalize, essential, evidence,
   explanation, explication, facsimile telegraph,
   faithful translation, fasten, fit, five-percenter, fix, fold,
   fold up, free translation, frequency, friend at court, gear to,
   geocentric, gloss, glossary, good influence, gray eminence, guide,
   harmonize, heavyweight, height, hidden hand, high pitch, hint,
   holm, homologate, homologize, horn, hot lead, hue, humor,
   important, indication, indicator, influence, influence peddler,
   influencer, ingroup, insularity, interlinear,
   interlinear translation, interrupter, intimation, island,
   island group, islandology, isle, islet, key signature, key to,
   key word, keynote, kingmaker, latch, latchkey, latchstring, lead,
   legend, level, lip, lobby, lobbyist, lock, lock out, lock up,
   loose translation, lords of creation, low pitch, main, major,
   major key, make plumb, make uniform, man of influence, manipulator,
   master key, measure, mediant, metaphrase, middle, middlemost,
   midmost, minor, mood, mouthpiece, multiplex telegraphy,
   natural color, necessary, new philharmonic pitch, news ticker,
   note, occlude, oceanic island, omphalic, open sesame, opener,
   padlock, pallor, paraphrase, passkey, password, pedal point,
   philharmonic pitch, philosophical pitch, pipe, pitch, pivotal,
   plumb, pony, powers that be, pressure group, proportion,
   put in tune, quadruplex telegraphy, railroad telegraphy, receiver,
   reconcile, rectify, reed, reef, register, regulate, restatement,
   rewording, right, sandbank, sandbar, scent, seal, seal off,
   seal up, secure, sender, set, set right, shade, shut,
   shut the door, shut up, similarize, simplex telegraphy,
   single-current telegraphy, sinister influence, skeleton key,
   skin color, slam, slide, snap, sounder, special interests,
   special-interest group, spoor, squeeze shut, standard pitch,
   stock ticker, strangle, style, subdominant, submarine telegraphy,
   submediant, subtonic, suggestion, supertonic, sync, synchronize,
   tailor, telegraphics, telegraphy, teleprinter, teletypewriter,
   teletypewriting, telex, telltale, tenor, the Establishment, ticker,
   ticket, timbre, tin opener, tinct, tincture, tinge, tint, tip-off,
   tonality, tone, tonic, tonic key, tooter, trace, transcription,
   translation, transliteration, transmitter, trim to, trot, true,
   true up, tune, typotelegraph, typotelegraphy, umbilical,
   undercolor, valve, very important person, vestige, vital,
   wheeler-dealer, whiff, wind, wind instrument, wire service,
   wire-puller, zip up, zipper



The Free On-line Dictionary of Computing (30 December 2018):

key
character key

   1.  A value used to identify a record in a
   database, derived by applying some fixed function to the
   record.  The key is often simply one of the fields (a
   column if the database is considered as a table with records
   being rows, see "key field").  Alternatively the key may be
   obtained by applying some function, e.g. a hash function, to
   one or more of the fields.  The set of keys for all records
   forms an index.  Multiple indexes may be built for one
   database depending on how it is to be searched.

   2.  A value which must be fed into the
   algorithm used to decode an encrypted message in order to
   reproduce the original plain text.  Some encryption schemes
   use the same (secret) key to encrypt and decrypt a message,
   but public key encryption uses a "private" (secret) key and
   a "public" key which is known by all parties.

   3.  An electromechanical keyboard button.

   (2003-07-04)


Easton's 1897 Bible Dictionary:

Key
   frequently mentioned in Scripture. It is called in Hebrew
   _maphteah_, i.e., the opener (Judg. 3:25); and in the Greek New
   Testament _kleis_, from its use in shutting (Matt. 16:19; Luke
   11:52; Rev. 1:18, etc.). Figures of ancient Egyptian keys are
   frequently found on the monuments, also of Assyrian locks and
   keys of wood, and of a large size (comp. Isa. 22:22).

     The word is used figuratively of power or authority or office
   (Isa. 22:22; Rev. 3:7; Rev. 1:8; comp. 9:1; 20:1; comp. also
   Matt. 16:19; 18:18). The "key of knowledge" (Luke 11:52; comp.
   Matt. 23:13) is the means of attaining the knowledge regarding
   the kingdom of God. The "power of the keys" is a phrase in
   general use to denote the extent of ecclesiastical authority.


Bouvier's Law Dictionary, Revised 6th Ed (1856):

KEY, estates. A wharf at which to land goods from, or to load them in a
vessel. This word is now generally spelled Quay, from the French, quai.