The Collaborative International Dictionary of English v.0.48:

Smother \Smoth"er\, v. t. [imp. & p. p. Smothered; p. pr. &
   vb. n. Smothering.] [OE. smotheren; akin to E. smoor. See
   Smoor.]
   1. To destroy the life of by suffocation; to deprive of the
      air necessary for life; to cover up closely so as to
      prevent breathing; to suffocate; as, to smother a child.
      [1913 Webster]

   2. To affect as by suffocation; to stife; to deprive of air
      by a thick covering, as of ashes, of smoke, or the like;
      as, to smother a fire.
      [1913 Webster]

   3. Hence, to repress the action of; to cover from public
      view; to suppress; to conceal; as, to smother one's
      displeasure.
      [1913 Webster]

WordNet (r) 3.0 (2006):

smothered
    adj 1: held in check with difficulty; "a smothered cough"; "a
           stifled yawn"; "a strangled scream"; "suppressed
           laughter" [syn: smothered, stifled, strangled,
           suppressed]
    2: completely covered; "bonnets smothered with flowers";
       "smothered chicken is chicken cooked in a seasoned gravy"

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "smothered":
   arcane, bated, cabalistic, censored, classified, close, closed,
   concealed, crushed, cryptic, damped, dampened, dark, dead,
   deadened, dull, dulled, enigmatic, esoteric, flat, hermetic,
   hidden, hush-hush, latent, muffled, muted, mysterious, occult,
   quashed, quelled, repressed, restricted, secret, smashed, softened,
   sordo, squashed, squelched, stifled, subdued, suffocated,
   suppressed, top secret, ulterior, unbreatheable, under security,
   under wraps, undisclosable, undisclosed, undivulgable, undivulged,
   unrevealable, unrevealed, unspoken, untellable, untold,
   unutterable, unuttered, unwhisperable