The phrase "a thingy" is correct and usable in written English, though it is informal.
You can use it when referring to an object or concept that is not specifically named or when the exact term is unknown or forgotten.
Example: "Can you pass me that thingy over there on the table?"
Alternatives: "a gadget" or "an item".
I remember waking up from the coma and there were four nurses wrestling with me, ramming a thingy up my knob.
If you are not familiar with object oriented programming, the dep object is just a thingy that stores all the information about the deprojection analysis (e.g. the source redshift, PHA file information and the source model definitions) as object attributes.
"And why should we?" cried Toryboy, puce with fury late one night after yet another futile attempt at coaxing a thingy that promises to read the barcodes of all the books in your home (and keep a meticulous record of them all in what we both still vaguely imagine to be literal, usually manila, tiny files and folders) out of the ether and on to his phone.
Also exhibiting herself in this freakfest is some Christian lady called Andrea Minichiello Williams (chief-exec of a thingy called Christian Concern and the Christian Legal Center).
In honor of the cause, the talk show host brought out Miley Cyrus to play a game of "Wrecking Balls," which involves moving a ball along the floor with a "thingy" dangling between your legs.
You drive a hover bike, a giant robot tank thingy, a jet, a boat that can submerge underwater at will.
The show was an amazing experience, except for the weekend food at Elstree Studios: a hard potato with an undressed salad in a polystyrene thingy.
If you have a mini whiteboard and a whiteboard marker and an eraser, get the whiteboard spinning and make a swirly thingy on the whiteboard.
It was a weird plastic ball filled with gooey fluid that had a triangle thingy floating in it.
To this day, the two refer to shoes as "thingies," and my friend calls to remind me when there's "a great thingy sale at Nordstrom's".
