A CrashBack is the recollection and reliving of a memory that involved an automotive accident, or crash.
The CrashBack is the minds eye experience you go through when recalling such an event.
"Damn, I just went past that road and had a crashback from four years ago.. that car hit my motorbike hard!"
- "You okay dude? you just went all quiet"
-- "What? Oh, I was having a crashback"
- "ah I often get those too..."