hush up
     v 1: cover up a misdemeanor, fault, or error; "Let's not
          whitewash the crimes of Stalin"; "She tried to gloss
          over her mistakes" [syn: {whitewash}, {gloss over}, {sleek
          over}]
     2: cause to be quiet or not talk; "Please silence the children
        in the church!" [syn: {hush}, {quieten}, {silence}, {still},
         {shut up}] [ant: {louden}]
Source: WordNet® 2.0