Noun: "(narratology) the technique, typically used in horror films and video games, of having something occur suddenly and without warning to frighten the audience"
They'd do something horrible, maybe kill off a few protagonists, and then make people sit around waiting for the next terrible thing to come along. They called it “setting up a jump scare.”
2011, John Landis, Monsters in the Movies: 100 years of Cinematic Nightmares, DK Publishing (2011), →ISBN, page 109:
JL: There was also one jump scare really[sic] got me in that film.
2011, John Rosenberg, The Healthy Edit: Creative Techniques for Perfecting Your Movie, Focal Press (2011), →ISBN, pages 80-81:
Drag Me to Hell capitalizes on the jump scare, scattering it liberally throughout the film to the point where it becomes almost numbing.
If this was a horror movie, the director totally would have done that as an easy jump scare.
2013, Jeffrey Bullins, "Hearing the Game: Sound Design", in To See the Saw Movies: Essays on Torture Porn and Post-9/11 Horror (ed. James Aston), McFarland & Company (2013), →ISBN, page 188:
This quiet is broken suddenly with an initial jump scare of the puppet's iconic laughter.