What is Missing Ship?

Legal Definition
Mar. law. When a ship or other vessel has been at sea for a much longer time than she ought to have been, she is presumed to have perished there with all on board, and such a vessel is called a missing ship.

2. There is no precise time fixed as to when the presumption is to arise, and this must depend upon the circumstances of each case. 2 Str. R. 1199; Park. Ins. 63; Marsh. Ins. 488; 2 Johns. R. 150; 1 Caines' R. 525; Holt's N. P. Rep. 242.
-- Bouviers Law Dictionary
Legal Definition
In maritime law. A vessel is so called when, computed from her known day of sailing, the time that has elapsed exceeds the average duration of similar voyages at the same season of the year. 2 Duer, Ins. 469.
-- Black's Law Dictionary
Legal Definition
A ship presumed lost from being long unheard of.
-- Ballentine's Law Dictionary