Source : Webster's Revised Unabridged Dictionary (1913)

Rapper \Rap"per\, n. [From {Rap}.]
   1. One who, or that which, raps or knocks; specifically, the
      knocker of a door. --Sterne.

   2. A forcible oath or lie. [Slang] --Bp. Parker.

Source : WordNet®

rapper
     n 1: someone who performs rap music
     2: a device (usually metal and ornamental) attached by a hinge
        to a door [syn: {knocker}, {doorknocker}]