The Collaborative International Dictionary of English v.0.48:

Hush \Hush\ (h[u^]sh), v. t. [imp. & p. p. Hushed (h[u^]sht);
   p. pr. & vb. n. Hushing.] [OE. huschen, hussen, prob. of
   imitative origin; cf. LG. hussen to lull to sleep, G. husch
   quick, make haste, be silent.]
   1. To still; to silence; to calm; to make quiet; to repress
      the noise or clamor of.
      [1913 Webster]

            My tongue shall hush again this storm of war.
                                                  --Shak.
      [1913 Webster]

   2. To appease; to allay; to calm; to soothe.
      [1913 Webster]

            With thou, then,
            Hush my cares?                        --Otway.
      [1913 Webster]

            And hush'd my deepest grief of all.   --Tennyson.
      [1913 Webster]

   To hush up, to procure silence concerning; to suppress; to
      keep secret. "This matter is hushed up." --Pope.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

hushed \hushed\ (h[u^]sht), adj.
   1. having the sound level reduced; -- especially used of the
      noise of conversation; as, speaking in hushed tones.

   Syn: muted.
        [WordNet 1.5]

   2. having relatively little noise; as, a hushed church.

   Syn: quiet.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

hushed
    adj 1: in a softened tone; "hushed voices"; "muted trumpets"; "a
           subdued whisper"; "a quiet reprimand" [syn: hushed,
           muted, subdued, quiet]

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "hushed":
   at rest, calm, chastened, cloistered, closet, confidential,
   constrained, controlled, cool, dwindling, ebbing, echoless,
   even-tenored, halcyon, hush as death, impassive, in control,
   in hand, inaudible, inside, isolated, limited, moldering, mousy,
   noiseless, pacific, peaceable, peaceful, placid, quelled,
   quiescent, quiet, reposeful, reposing, restful, resting,
   restrained, secluded, sequestered, sequestrated, sheltered, silent,
   smooth, softened, soundless, stable, still, still as death,
   stillish, stilly, stoic, stolid, subaudible, subdued, subsiding,
   tempered, tranquil, unagitated, unarticulated, undisturbed,
   unhearable, unmoved, unperturbed, unpronounced, unruffled,
   unsounded, unstirring, untroubled, unuttered, unvocalized,
   unvoiced, waning, whist