To bypass all the jokes about what discharged, and what it took to cure the discharge-
No. Have never seen a firearm fire a cartridge without some outside force. The force is USUALLY a finger on the trigger when it should not be (keep yer booger hook off'n the bangswitch) RARELY has the force been a foreign object (twig inside trigger guard, dog pawing at a cocked shotgun)
The cookoff mentioned is when a weapon has been fired over and over- and the heat of the weapon causes powder in chambered cartridge to ignite. Have only seen in a smokin' hot full auto (one of the reasons many full autos are open bolt guns) Don't think is possible to get a revolver that hot.
Now, in fairness, the ORIGINAL single action revolver COULD fire if hammer was resting on a cartridge, and the hammer were struck with sufficient force, or if gun were dropped and landed on hammer. Design has been changed to keep that from happening with modern arms.
Last ND I saw, weapon was being replaced in holster- with finger ON THE TRIGGER. Holster pushed finger on trigger, gun did what it was designed to do- went BANG.