weed out

To weed out is to remove the specific things you don’t want from a group of items, like when you weed out your paperbacks, leaving only hardcover books on your shelf.

This idiom comes from the verb weed, which means “remove weeds from a garden.” When you weed out something, you similarly take away the unwanted or unpleasant things (or in some cases, people). When choosing the students to represent your class at an all-school assembly, your teacher might weed out the kids who hate public speaking.