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):

suppress
    v 1: to put down by force or authority; "suppress a nascent
         uprising"; "stamp down on littering"; "conquer one's
         desires" [syn: suppress, stamp down, inhibit,
         subdue, conquer, curb]
    2: come down on or keep down by unjust use of one's authority;
       "The government oppresses political activists" [syn:
       oppress, suppress, crush]
    3: control and refrain from showing; of emotions, desires,
       impulses, or behavior [syn: inhibit, bottle up,
       suppress]
    4: put out of one's consciousness [syn: suppress, repress]
    5: reduce the incidence or severity of or stop; "suppress a
       yawn"; "this drug can suppress the hemorrhage"

Moby Thesaurus II by Grady Ward, 1.0:

239 Moby Thesaurus words for "suppress":
   abate, absorb the shock, allay, alleviate, annihilate, arrest,
   asphyxiate, assuage, attemper, ban, bank the fire, bar, beat down,
   bend, black out, block, blunt, bottle up, break, break down,
   break the fall, bring low, bring to terms, browbeat, bulldoze,
   bully, castrate, cease, censor, chasten, check, choke, choke off,
   clamp down on, coerce, compel, conceal, conquer, constrain,
   control, cork, cork up, countercheck, cover up, cow, crack down on,
   crush, curb, cushion, cut off, dam up, damp, damp down, dampen,
   daunt, de-emphasize, deaden, debar, delay, deny, despotize, detain,
   diminish, disallow, discontinue, domineer, domineer over, downplay,
   drown, dull, dwarf, embargo, end, enjoin, enslave, exclude,
   exclude from, extenuate, extinguish, fell, flatten, forbid, gag,
   grind, grind down, halt, henpeck, hide, hinder, hold back,
   hold down, hold in, hold in check, hold up, hugger-mugger, humble,
   humiliate, hush, hush up, hush-hush, impede, inhibit, intercept,
   interdict, interfere, intermeddle, interrupt, intervene,
   intimidate, jump on, keep, keep back, keep down, keep in,
   keep in check, keep quiet, keep secret, keep under,
   keep under control, keep within bounds, kill, lay, lenify, lessen,
   lighten, lock in, lord it over, maintain, master, meddle, mitigate,
   moderate, modulate, muffle, mute, muzzle, neutralize, obstruct,
   obtund, offset, oppose, oppress, outlaw, overawe, overbear,
   overmaster, override, overwhelm, palliate, play down,
   pour water on, preclude, preserve, press heavy on, prevent,
   prohibit, proscribe, prostrate, put, put down, put out, quash,
   quell, quench, quiet, reduce, reduce the temperature, refuse,
   reject, repress, resist, restrain, retain, retard, ride down,
   ride over, ride roughshod over, rule out, save, save up, say no to,
   scotch, set back, show consideration, show mercy, show pity, shush,
   shut down on, shut out, silence, sit down on, sit on, slacken,
   slow down, smash, smother, snub, snuff out, sober, sober down,
   soften, soften the blow, squash, squelch, stamp out, stanch,
   stifle, stop, strangle, stultify, subdue, subjugate, sublimate,
   suffocate, taboo, tame, temper, terminate, terrorize, throttle,
   tone down, trample down, trample out, trample underfoot,
   trample upon, tread down, tread underfoot, tread upon, tune down,
   tyrannize, tyrannize over, underplay, unman, vanquish,
   walk all over, walk over, weaken, weigh heavy on, withhold