whatchamacallit

Noun

• something unspecified whose name is either forgotten or not known
  • she eased the ball-shaped doodad back into its socket
    
  • there may be some great new gizmo around the corner that you will want to use
    

Related words

• Synonyms: 
  doodad , doohickey , doojigger , gimmick , gizmo , gismo , gubbins , thingamabob , thingumabob , thingmabob , thingamajig , thingumajig