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]

WordNet (r) 3.0 (2006):

hickey
    n 1: a small inflamed elevation of the skin; a pustule or
         papule; common symptom in acne [syn: pimple, hickey,
         zit]
    2: a temporary red mark on a person's skin resulting from
       kissing or sucking by their lover [syn: hickey, love
       bite]

Moby Thesaurus II by Grady Ward, 1.0:

93 Moby Thesaurus words for "hickey":
   affair, article, artifact, birthmark, blackhead, bleb, blemish,
   blister, bulla, check, cicatrix, comedo, crack, crater, craze,
   defacement, defect, deformation, deformity, dingus, disfiguration,
   disfigurement, distortion, dofunny, dohickey, dojigger, dojiggy,
   domajig, domajigger, doodad, dowhacky, eppes, etwas, fault, flaw,
   flumadiddle, freckle, gadget, gigamaree, gimmick, gizmo,
   hemangioma, hootenanny, hootmalalie, jigger, keloid, kink, lentigo,
   material thing, milium, mole, needle scar, nevus, object, pimple,
   pit, pock, pockmark, port-wine mark, port-wine stain, pustule,
   quelque chose, rift, scab, scar, scratch, sebaceous cyst,
   something, split, strawberry mark, sty, thing, thingum,
   thingumabob, thingumadad, thingumadoodle, thingumajig,
   thingumajigger, thingumaree, thingummy, track, twist, verruca,
   vesicle, wale, warp, wart, weal, welt, wen, whatchy, whitehead,
   widget