unavoidable casualty

noun

1. : unavoidable accident; also : an unavoidable circumstance that prevents the timely performance of a procedural act (as the filing of an answer) by a party or the party's lawyer — compare excusable neglect : an unavoidable circumstance that prevents the timely performance of a procedural act (as the filing of an answer) by a party or the party's lawyer — compare excusable neglect

   Note: As with excusable neglect, showing evidence of unavoidable casualty will relieve a party from a default judgment or a time limit.