Whatchamacallit
A word used when the actual name of the object in question will not come to mind. Very versatile but often very vague. It is derived from the phrase "what-you-may-call-it" which can be found in T. H. White's The Once and Future King.
Claire- "Hey, Adam, hand me the- the- you know, the whatchamacallit."

Adam- "The what?"
