rap·per /ˈræpɚ/
  敲頂錘; 輕敲錘; 松模工具
  Rap·per n.
  1. One who, or that which, raps or knocks; specifically, the knocker of a door.
  2. A forcible oath or lie. [Slang]
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  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]