Meaning of whachamacallit

wha•cha•ma•call•it

Pronunciation: (hwuch'u-mu-kôl"it, hwoch'-, wuch'-, woch'-), [key]
— n. Informal.
  1. an object or person whose name one does not know or cannot recall.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.