Source : Webster's Revised Unabridged Dictionary (1913)

Deafening \Deaf"en*ing\, n.
   The act or process of rendering impervious to sound, as a
   floor or wall; also, the material with which the spaces are
   filled in this process; pugging.

Deafen \Deaf"en\, v. t. [imp. & p. p. {Deafened}; p. pr. & vb.
   n. {Deafening}.] [From {Deaf}.]
   1. To make deaf; to deprive of the power of hearing; to
      render incapable of perceiving sounds distinctly.

            Deafened and stunned with their promiscuous cries.
                                                  --Addison.

   2. (Arch.) To render impervious to sound, as a partition or
      floor, by filling the space within with mortar, by lining
      with paper, etc.

Source : WordNet®

deafening
     adj : loud enough to cause (temporary) hearing loss [syn: {earsplitting},
            {roaring}, {thunderous}, {thundery}]