The phrase "unexplained death" means that someone has died, but the cause of their death is not immediately known or understood. It requires further investigation to determine why the person died. Full definition
Fierro, the Virginia forensic pathologist, called Oklahoma's decision not to look carefully into unexplained deaths of residents over 40 a mistake. (scientificamerican.com)
Patients with epilepsy and, in particular, those with severe syndromic forms of the disorder, harbor a risk of sudden unexplained death in epilepsy, or SUDEP. (sciencedaily.com)
As a postdoctoral fellow, Auerbach studied the heart - brain connection in a severe genetic form of epilepsy, and found that cardiac arrhythmias were one cause of sudden unexplained death in people with epilepsy. (sciencedaily.com)