A lame, cheap trick usually used on cartoons that originated on the show Scooby-Doo. It's where the main characters are being chased my something, usually only one but sometimes more. The characters are seen running back and forth through three sets of doors/doorway-like-things, three on the left and three on the right. Done in silence except for special effects.
It's so annoying when that every time there's a chasing scene in a cartoon, they pull out the scooby-doo run.