1. to have a wreck. The plane cracked up and killed two of the passengers. Whose car cracked up on the expressway?
2. to break out in laughter. The whole audience cracked up. I knew I would crack up during the love scene.
3. Sl. to have a mental or emotional breakdown. The poor guy cracked up. It was too much for him. You would crack up, too, if you had been through all he went through.
4. an accident; a wreck. (Usually crack-up.) There was a terrible crack-up on the expressway. There were four cars in the crack-up.
See also: crack, up