Its an abnormal low-resistance connection between two nodes of an electrical circuit that are meant to be at different voltages.
Not necessarily. A "short" is when, for some reason, you have an abnormally low resistance in a circuit which results in an extremely high current flow almost instantly. Now, a common cause of that is the failure of electrical insulation in a circuit and the increase in current is so much it will cause excess heat which could cause the insulation on adjacent cabling to fail, leading to an overvoltage in a lower voltage circuit as you describe as bare cables decide to touch each other.
The cause of the original degradation could be many, of which an overvoltage from a lightning strike is one, but not the only, cause.
Let's just wait on the reports, shall we.