A tactic used in horror movies to scare people, the jump scare is used by unimaginative filmmakers as a cheap method of frightening the audience; i.e, making them literally "jump" out of their seats. This device is being increasingly employed in modern horror movies, along with gratuitous amounts of gore, because the directors have forgotten how to actually scare people.
A scantily clad, bosomy teenager who hears a suspicious noise in her empty house on a rainy night while watching a movie gets up from the couch to investigate its source. Walking slowly, she calls out, "Is anybody there?" As she nears the kitchen, a black cat streaks across the hallway, accompanied by a loud, piercing measure of orchestral music. "Oh, whiskers, you silly cat, you scared me!" she says, breathing a sigh of relief. She turns around, anxious to get back to her movie, when an axe suddenly buries itself in her skull.
Most of the audience screams in fright. However, the veteran horror movie fans in the theater have seen way too many cheap uses of the jump scare to be fooled. They shake their heads and think about the good old days when movies like The Shining were actually able to genuinely scare them.