When something screeches, it makes a very loud, high-pitched noise that hurts your ears.
Screeches are usually annoying or scary because they are so loud and unpleasant.
Examples:
The car screeches to a stop.
The owl screeches at night.
The little girl screeches when she sees a spider.
The microphone screeches when it's too close to the speaker.
The brakes screeches loudly, making everyone jump.
The cat screeches when it doesn't want to take a bath.