a failure or collapse, an instance of something breaking down and no longer functioning, sometimes figuratively as a person's mental or emotional state;
e.g. The system underwent a crack-up, and they were forced to rebuild everything anew. She suffered a crack-up after the accident.
(noun)
an instance of destruction or wreckage, usually caused by a crash or collision;
e.g. We were delayed by a crack-up in the middle of the road.