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.
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            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:

Hushing \Hush"ing\, n. (Mining)
   The process of washing ore, or of uncovering mineral veins,
   by a heavy discharge of water from a reservoir; flushing; --
   also called booming and hydraulic mining.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

hushing
    n 1: a fricative sound (especially as an expression of
         disapproval); "the performers could not be heard over the
         hissing of the audience" [syn: hiss, hissing,
         hushing, fizzle, sibilation]