The Collaborative International Dictionary of English v.0.48:

Suppress \Sup*press"\, v. t. [imp. & p. p. Suppressed; p. pr.
   & vb. n. Suppressing.] [L. suppressus, p. p. of supprimere
   to suppress; sub under + premere, pressum, to press. See
   Sub-, and Press.]
   1. To overpower and crush; to subdue; to put down; to quell.
      [1913 Webster]

            Every rebellion, when it is suppressed, doth make
            the subject weaker, and the prince stronger. --Sir
                                                  J. Davies.
      [1913 Webster]

   2. To keep in; to restrain from utterance or vent; as, to
      suppress the voice; to suppress a smile. --Sir W. Scott.
      [1913 Webster]

   3. To retain without disclosure; to conceal; not to reveal;
      to prevent publication of; as, to suppress evidence; to
      suppress a pamphlet; to suppress the truth.
      [1913 Webster]

            She suppresses the name, and this keeps him in a
            pleasing suspense.                    --Broome.
      [1913 Webster]

   4. To stop; to restrain; to arrest the discharges of; as, to
      suppress a diarrhea, or a hemorrhage.
      [1913 Webster]

   Syn: To repress; restrain; put down; overthrow; overpower;
        overwhelm; conceal; stifle; stop; smother.
        [1913 Webster]

WordNet (r) 3.0 (2006):

suppressed
    adj 1: kept from public knowledge by various means; [ant:
           publicised, publicized]
    2: manifesting or subjected to suppression; "a suppressed press"
    3: held in check with difficulty; "a smothered cough"; "a
       stifled yawn"; "a strangled scream"; "suppressed laughter"
       [syn: smothered, stifled, strangled, suppressed]

Moby Thesaurus II by Grady Ward, 1.0:

125 Moby Thesaurus words for "suppressed":
   Lethean, Olympian, absentminded, aloof, amnestic, arcane, backward,
   bashful, blank, blocked, bond, broken, cabalistic, captive,
   censored, chilled, chilly, classified, close, closed, cold,
   concealed, conquered, constrained, converted, cool, crushed,
   cryptic, dark, detached, discreet, disenfranchised, distant,
   enigmatic, enslaved, enthralled, esoteric, expressionless, felled,
   flattened, forbidding, forgetful, forgetting, frigid, frosty,
   guarded, heedless, hermetic, hidden, humbled, hush-hush, icy,
   impassive, impersonal, in bondage, in bonds, in captivity,
   in chains, in slavery, in subjection, inaccessible,
   inclined to forget, introverted, latent, mastered, modest,
   mysterious, oblivious, occult, offish, oppressed, put down,
   quashed, quelled, reduced, remote, removed, repressed, reserved,
   restrained, restricted, reticent, retiring, secret, shrinking,
   smashed, smothered, squashed, squelched, standoff, standoffish,
   stifled, subdued, subjected, subjugated, suffocated, top secret,
   ulterior, unaffable, unapproachable, unbreatheable, uncongenial,
   undemonstrative, under security, under the heel, under the lash,
   under wraps, undisclosable, undisclosed, undivulgable, undivulged,
   unexpansive, unfree, ungenial, unmindful, unrevealable, unrevealed,
   unspoken, untellable, untold, unutterable, unuttered,
   unwhisperable, vanquished, withdrawn