What does Revelation 18:8 mean?

According to this verse, Babylon—a corrupt and ungodly culture or political entity—will end abruptly. Her destruction will be sudden, not gradual. It will be decisive and terrifying.

In the end times, the demise of this symbolic Babylon will be as surprising and sudden as the death of King Belshazzar. He profaned the temple's sacred vessels, was opulent, immoral, and egotistical. However, while he and a thousand of his lords were partying, a hand appeared on the plaster of the palace wall. The terrifying sight caused him great alarm, and he sought someone to interpret the writing. After his wise men failed to interpret the writing, Daniel was fetched to do so. He announced that the writing spelled the end of Belshazzar's kingdom. That same night the party was over; Belshazzar was killed (Daniel 5).

In a moment, "the party" will end for Babylon as well. Her plagues will come in a single day. Death, mourning, and famine will strike her, and she will be consumed with fire. The Lord will show in His judgment that He is mighty and she is merely finite.