The Collaborative International Dictionary of English v.0.48:

hickey \hick"ey\, hickie \hick"ie\n.
   1. (Elec.) A device used to adapt a lighting fixture for
      mounting in an outlet box, or on a pipe.
      [PJC]

   2. A red mark on the skin, caused by a passionate, sucking
      kiss at that location. [slang]
      [PJC]

   3. a doohickey. [informal]
      [PJC]