Wiktionary
n. An inflatable bag containing a valve at its neck that retains the air in the bag until pressure is put on it (usually by someone unintentionally sitting on it after it has been placed on a chair by someone else as a practical joke), when the air is expelled with a sound similar to that of someone break wind.
Wikipedia
A whoopee (or whoopie) cushion, also known as a farting bag, windy blaster, poo-poo cushion, and Razzberry Cushion, is a practical joke device involving flatulence humour, which produces a noise resembling a " raspberry" or human flatulence. It is made from two sheets of rubber that are glued together at the edges. There is a small opening with a flap at one end for air to enter and leave the cushion.
To use it, one must first inflate it with air, then place it on a chair or squeeze it. Some whoopee cushions can be self-inflating. If placed on a chair, an unsuspecting victim will sit on the whoopee cushion, forcing the air out of the opening, which causes the flap to vibrate and create a loud, flatulence-like sound.
Such similar noise can also be made with an inflated rubber balloon, by releasing the opening and letting it deflate. The escaping air causes the opening to vibrate and make noise as the balloon is propelled away.
Usage examples of "whoopee cushion".
Three balls for a dollar, and whoever scores on the target makes Brown fall on the biggest, loudest, smelliest whoopee cushion ever put out by the Ack-Mee Novelty Company!
No one would have believed, before a pair of simian hands had worked on the project, that something like Doinov's romantic Prelude in G could be rescored for Whoopee Cushion and Squashed Rabbits.
It wasBlake who owned a whoopee cushion that emittedrude noises when sat upon.
Mr Wintler, a man of the variety that thinks a whoopee cushion is the last word in repartee, was not the kind to let a mere freezing reception stand in his way.
Not looking behind her, Cameron collapsed heavily on to a whoopee cushion which Tab had slipped on to her chair, and which let out a succession of noisy farts.
Believing that Zeus, or Odin, or Shiva could find themselves on the cosmic whoopee cushion every now and then just like Uncle Cheng probably made the night seem a little less dark, the vastness of space and time a smidgen less overbearing.
Beverly Marsh had shown up around three o'clock, wearing faded jeans and toting a very old Daisy air rifle that had lost most of its pop - when you pulled its tape-wrapped trigger, it uttered a wheeze that sounded to Richie more like someone sitting on a very old Whoopee Cushion than a rifleshot.
The snores flapping through his lips sounded like a whoopee cushion, flat and wet.
Patrick's day you don't dare sit down without looking for a green whoopee cushion.
It was hard to believe Athaclena came from the same stock as the author of this little bit of whoopee cushion humor.
I'm told that the plastic object underneath the missile launcher is an, ah, whoopee cushion.
Luckily for us, that charming old party Charles Burnside, who can always be depended upon to slip a whoopee cushion under the governor's seat during a banquet, to pour a little hot sauce into the stew, to fart at the prayer meeting, is at this moment emerging from a toilet bowl and into a stall in the men's room on Daisy wing.