noun. A thingama-hoo-whacker.
Real citation: "If Donnah finds a pic of DA in a chenille elastic midriff whatchama-doo-jobby, and posts it, I will go on some kind of rampage, and it will not be pretty."
(Aug. 15, 2008, Florida Cracker, http://www.florida-cracker.org/archives/004504.html)
Made-up citation: "If you're not satisifed with your whatchama-doo-jobby, try our new green-glowing-nano-slime-ammo-pack. Our promise to you: it does not remotely taste like Grandma."