watchamacallit Share definition Flag A word used to replace a word that you don't know. "Doohickey" and "thingamajig" are equivalents. You just push the button on the watchamacallit, then it's ready! watchamacallit by th100 May 27, 2010 0 0 Get merch Get the watchamacallit mug. Buy Now — $32.95 See more merch