To berate someone means to scold them harshly and at length, criticizing them severely for something they did wrong. When a coach berates a player, he doesn't just say “that was a mistake.” Instead, he delivers a long, angry lecture about how careless the player was. When a customer berates a waiter over a small error, she goes on and on about how terrible the service was, making the person feel awful.

The word suggests criticism that goes beyond what's necessary or fair. If you forget your homework and your teacher calmly reminds you to be more responsible, that's not berating. But if someone spends ten minutes loudly telling you how irresponsible, careless, and thoughtless you are, that's berating. The anger and the length of the criticism are what make it harsh.

People sometimes berate themselves, too, replaying their mistakes in their minds and being overly critical. A student who berates herself for missing one question on a test is being too harsh on herself.