Informal Something difficult to classify or whose name has been forgotten or is not known. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "thingamajig" in a sentence
"Apparently, the forcefield thingamajig is some kind of gadget for analyzing contractor abilities, but alas, Hei’s powers are incapable of being analyzed, causing the gadget to fail."
"One opposition member has already said he suspects the premier will simply come up with some diversionary tactic - a "thingamajig" - aimed at pacifying the public."
"She has some kind of thingamajig like this that helps her ..."