In the United States, some telephone area codes were split or overlaid immediately, rather than being phased in with a permissive dialing period.
An example is telephone area code 213, which serves downtown Los Angeles and its immediate environs, split in January 1951 into 213 and 714 all at once.
A flash cut can also define a procedure in which multiple components of computer infrastructure are upgraded in multiple ways, all at once, with no phase-in period.
In film, an extremely brief shot, sometimes as short as one frame, which is nearly subliminal in effect.
Also a series of short staccato shots that create a rhythmic effect.