- If you are insane you can not think well because of mental illness.
- He was sent to a mental hospital because he was insane.
- Nothing he signed can be used because he was insane when he signed.
- An insane idea is very strange, like something a crazy person might think of.
- That has got to be the most insane thing I have ever heard.
- If something is insane it does not make sense. It is strange in a bad way.
- The price of gas these days is insane.