An unforeseen accident or Act of G-d, e.g. a fire, tsunami, earthquake, plane crash. Also may refer to the loss or the liability that is incurred as a result of the incident.
Law Dictionary – Alternative Legal Definition
Inevitable accident; an event not to be foreseen or guarded against. A loss from such an event or cause; as by fire, shipwreck, lightning, etc. Casualties of superiority. In Scotch law. Payments from an inferior to a superior, that is, from a tenant to his lord, which arise upon uncertain events, as opposed to the payment of rent at fixed and stated times. Bell. Casualties of wards. In Scotch law. The mails and duties due to the superior in ward holdings.