Source : Webster's Revised Unabridged Dictionary (1913)

Obstreperous \Ob*strep"er*ous\, a. [L. obstreperus, from
   obstrepere to make a noise at; ob (see {Ob-}) + strepere to
   make a noise.]
   Attended by, or making, a loud and tumultuous noise;
   clamorous; noisy; vociferous. ``The obstreperous city.''
   --Wordsworth. ``Obstreperous approbation.'' --Addison.

         Beating the air with their obstreperous beaks. --B.
                                                  Jonson.
   -- {Ob*strep"er*ous*ly}, adv. -- {Ob*strep"er*ous*ness}, n.

Source : WordNet®

obstreperousness
     n : noisy defiance