the terrible twos
A developmental stage of children, generally at or around the age of two, marked by increased rebelliousness and frequent tantrums. Becca's been having really bad temper tantrums lately and just keeps saying "no" to everything we say to her. I guess she's going into the terrible twos.
a mind is a terrible thing to waste
Education and exercising one's mind is important. No, you absolutely must go to college after you graduate in the spring! A mind is a terrible thing to waste!
enfant terrible
A famous person who is known to behave inappropriately, often to others' shock or horror. As this phrase is French for "terrible child," it is typically pronounced with a French accent. If you continue to have tantrums on the court, you will be known as the enfant terrible of tennis. He is the enfant terrible of high society, so of course he wore blue jeans to the gala.