What is the difference in meaning between a crash and an accident ?

Accidents happens due to some unavoidable circumstances while crashes/collision occurs due to carelessness.

Explanation:

An accident is always an incident taking place without any intention to do so. Hence, all cases of accidents are unavoidable and could not be prevented under natural circumstances. Here the driver has taken all necessary measures for safe driving but yet the accident happens. such as blowing off Tyre when a sharp object protrude into it, extreme glaring on road that some how disturbed the focus of driver , etc.

While Crashes occur out of careless and hence most of the crashes/collision are avoidable and preventable. They are sometimes referred to as intended action because the driver knew that his/her act is going to be risky one but yet he/she continue driving for example driving sleep deprived or driving after alcohol consumption.