Crazy describes something wildly unreasonable, impractical, or out of control. When your friend suggests riding bicycles to a city three states away, you might say “That's a crazy idea!” because it wouldn't actually work. A crazy plan might sound exciting at first but falls apart when you think it through.

The word also means mentally ill or unable to think clearly, though using it this way about real people is unkind. Historically, people used “crazy” to dismiss or mock those with mental health conditions, which caused real harm. Today we understand that mental illness deserves the same respect and medical care as physical illness.

In casual conversation, people often use crazy to mean extremely enthusiastic or intense. Someone crazy about basketball might practice for hours every day. A crazy thunderstorm could mean one with dramatic lightning and pounding rain. Your classroom might go crazy with excitement when the teacher announces a field trip.

The phrase like crazy means doing something with extreme effort or intensity: “She studied like crazy for the spelling bee” means she prepared with total dedication.

Because crazy can be hurtful when describing people, consider using more precise words instead: “unrealistic,” “impractical,” “chaotic,” or “intense” often express what you mean more clearly.