The Collaborative International Dictionary of English v.0.48:

Secret \Se"cret\, a. [F. secret (cf. Sp. & Pg. secreto, It.
   secreto, segreto), fr. L. secretus, p. p. of secernere to put
   apart, to separate. See Certain, and cf. Secrete,
   Secern.]
   1. Hidden; concealed; as, secret treasure; secret plans; a
      secret vow. --Shak.
      [1913 Webster]

            The secret things belong unto the Lord our God; but
            those things which are revealed belong unto us.
                                                  --Deut. xxix.
                                                  29.
      [1913 Webster]

   2. Withdrawn from general intercourse or notice; in
      retirement or secrecy; secluded.
      [1913 Webster]

            There, secret in her sapphire cell,
            He with the Nais wont to dwell.       --Fenton.
      [1913 Webster]

   3. Faithful to a secret; not inclined to divulge or betray
      confidence; secretive. [R.]
      [1913 Webster]

            Secret Romans, that have spoke the word,
            And will not palter.                  --Shak.
      [1913 Webster]

   4. Separate; distinct. [Obs.]
      [1913 Webster]

            They suppose two other divine hypostases superior
            thereunto, which were perfectly secret from matter.
                                                  --Cudworth.
      [1913 Webster]

   Syn: Hidden; concealed; secluded; retired; unseen; unknown;
        private; obscure; recondite; latent; covert;
        clandestine; privy. See Hidden.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Secret \Se"cret\, n. [F. secret (cf. Pr. secret, Sp. & Pg.
   secreto, It. secreto, segreto), from L. secretum. See
   Secret, a.]
   1. Something studiously concealed; a thing kept from general
      knowledge; what is not revealed, or not to be revealed.
      [1913 Webster]

            To tell our own secrets is often folly; to
            communicate those of others is treachery. --Rambler.
      [1913 Webster]

   2. A thing not discovered; what is unknown or unexplained; a
      mystery.
      [1913 Webster]

            All secrets of the deep, all nature's works.
                                                  --Milton.
      [1913 Webster]

   3. pl. The parts which modesty and propriety require to be
      concealed; the genital organs.
      [1913 Webster]

   In secret, in a private place; in privacy or secrecy; in a
      state or place not seen; privately.
      [1913 Webster]

            Bread eaten in secret is pleasant.    --Prov. ix.
                                                  17.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Secret \Se"cret\, v. t.
   To keep secret. [Obs.] --Bacon.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

classified \classified\ adj.
   1. arranged into classes or categories; as, unclassified.

   Syn: categorized.
        [WordNet 1.5 +PJC]

   2. assigned to a class of documents withheld from general
      circulation; -- of information or documents. Opposite of
      unclassified.

   Note: [Narrower terms: eyes-only; confidential;
         restricted; secret; sensitive; top-secret]
         [WordNet 1.5]

WordNet (r) 3.0 (2006):

secret
    adj 1: not open or public; kept private or not revealed; "a
           secret formula"; "secret ingredients"; "secret talks"
    2: conducted with or marked by hidden aims or methods;
       "clandestine intelligence operations"; "cloak-and-dagger
       activities behind enemy lines"; "hole-and-corner intrigue";
       "secret missions"; "a secret agent"; "secret sales of arms";
       "surreptitious mobilization of troops"; "an undercover
       investigation"; "underground resistance" [syn: clandestine,
       cloak-and-dagger, hole-and-corner(a), hugger-mugger,
       hush-hush, secret, surreptitious, undercover,
       underground]
    3: not openly made known; "a secret marriage"; "a secret bride"
       [syn: unavowed, secret]
    4: communicated covertly; "their secret signal was a wink";
       "secret messages"
    5: not expressed; "secret (or private) thoughts" [syn: secret,
       private]
    6: designed to elude detection; "a hidden room or place of
       concealment such as a priest hole"; "a secret passage"; "the
       secret compartment in the desk" [syn: hidden, secret]
    7: hidden from general view or use; "a privy place to rest and
       think"; "a secluded romantic spot"; "a secret garden" [syn:
       privy, secluded, secret]
    8: (of information) given in confidence or in secret; "this
       arrangement must be kept confidential"; "their secret
       communications" [syn: confidential, secret]
    9: indulging only covertly; "a secret alcoholic"
    10: having an import not apparent to the senses nor obvious to
        the intelligence; beyond ordinary understanding; "mysterious
        symbols"; "the mystical style of Blake"; "occult lore"; "the
        secret learning of the ancients" [syn: mysterious,
        mystic, mystical, occult, secret, orphic]
    11: the next to highest level of official classification for
        documents
    n 1: something that should remain hidden from others (especially
         information that is not to be passed on); "the combination
         to the safe was a secret"; "he tried to keep his drinking a
         secret"
    2: information known only to a special group; "the secret of
       Cajun cooking" [syn: secret, arcanum]
    3: something that baffles understanding and cannot be explained;
       "how it got out is a mystery"; "it remains one of nature's
       secrets" [syn: mystery, enigma, secret, closed book]

Moby Thesaurus II by Grady Ward, 1.0:

190 Moby Thesaurus words for "secret":
   abstract, abstruse, arcane, arcanum, beclouded, behind the curtain,
   behind the scenes, blind, buried, by stealth, cabala, cabalistic,
   camouflaged, censored, clandestine, classified,
   classified information, close, closed, closemouthed, clouded,
   concealed, confidence, confidential, confidential communication,
   confidentially, covered, covert, cryptic, cryptographic, dark,
   deep, deep-seated, devious, discreet, disguised, eclipsed,
   encrypted, enigma, enigmatic, esoteric, esoterica, evasive,
   furtive, furtively, genitals, guarded secret, heavy, hermetic,
   hermetics, hid, hidden, hole-and-corner, hugger-mugger, hush-hush,
   immanent, imperceptible, implanted, implicit, in a cloud, in a fog,
   in eclipse, in purdah, in secret, in the wings, inalienable,
   incommunicado, incomprehensible, indiscernible, indwelling,
   infixed, ingrained, inherent, inner, insensible, internal,
   intrinsic, invisible, inward, inwrought, irreducible, latent,
   lonesome, mysterious, mystery, mystery of mysteries, mystical,
   obfuscated, obscure, obscured, occult, on the sly, out of sight,
   out-of-the-way, parts, personal matter, private, private matter,
   private parts, privately, privates, privileged communication,
   privity, privy, privy parts, profound, profound secret, pudenda,
   quiet, quietly, recondite, remote, removed, resident, restricted,
   restricted information, retired, screened, sealed book, secluded,
   secluse, secretive, secretly, sequestered, shifty, shrouded,
   sightless, smothered, sneak, stealthily, stealthy, stifled,
   subjective, submerged, suppressed, surreptitious, surreptitiously,
   the occult, top secret, top-secret, transcendental, ulterior,
   unacknowledged, unalienable, unapparent, unbeheld, unbeholdable,
   unbreatheable, unchallengeable, uncommunicative, undeclared,
   under an eclipse, under cover, under house arrest, under security,
   under wraps, under-the-table, undercover, underground, underhand,
   underhanded, underneath, undiscernible, undisclosable, undisclosed,
   undivulgable, undivulged, unknown, unnoticed, unobserved,
   unperceivable, unperceived, unpublishable, unpublished,
   unquestionable, unrealized, unrevealable, unrevealed, unseeable,
   unseen, unspoken, untellable, untold, unutterable, unuttered,
   unviewed, unwhisperable, unwitnessed, viewless,
   wrapped in clouds



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

SECRET, rights. A knowledge of something which is unknown to others, out of
which a profit may be made; for example, an invention of a machine, or the
discovery of the effect of the combination of certain matters.
     2. Instances have occurred of secrets of that kind being kept for many
years, but they are liable to constant detection. As such secrets are not
property, the possessors of them in general prefer making them public, and
securing the exclusive right for years, under the patent laws, to keeping
them in an insecure manner, without them. See Phil. on Pat. ch. 15; Gods. on
Pat. 171; Dav. Pat. Cas. 429; 8 Ves. 215; 2 Ves. & B. 218; 2 Mer. 446; 3
Mer. 157; 1 Jac. & W. 394; 1 Pick. 443; 4 Mason, 15; 3 B. & P. 630.



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

SECRET. That which is not to be revealed.
     2. Attorneys and counsellors, who have been trusted professionally with
the secrets of their clients, are not allowed to reveal them in a court of
justice. The right of secrecy belongs to the client, and not to the attorney
and counsellor.
     3. As to the matter communicated, it extends to all cases where the
client applies for professional advice or assistance; and it does not appear
that the protection is qualified by any reference to proceedings pending or
in contemplation. Story, Eq. Pl. Sec. 600; 1 Milne & K. 104; 3 Sim. R. 467.
     3. Documents confided professionally to the counsel cannot be demanded,
unless indeed the party would himself be bound to produce them. Hare on
Discov. 171. Grand jurors are sworn the commonwealth's secrets, their
fellows and their own to keep. Vide Confidential communications; Witness.