To cough down

from The Collaborative International Dictionary of English v.0.48

Cough \Cough\, v. t.
   1. To expel from the lungs or air passages by coughing; --
      followed by up; as, to cough up phlegm.
      [1913 Webster]

   2. To bring to a specified state by coughing; as, he coughed
      himself hoarse.
      [1913 Webster]

   {To cough down}, to silence or put down (an objectionable
      speaker) by simulated coughing.
      [1913 Webster]