Hardtack is a type of BISCUIT or cracker that has been around for centuries. It is made from flour, water, and sometimes salt, and is usually baked twice to make it hard and durable. The term 'hardtack' is often used to refer to any type of BISCUIT or cracker that is hard and dry. The crossword solutions for the term 'hardtack' include 'BISCUIT' (7 letters), 'seabiscuit' (10 letters), and 'shipbiscuit' (11 letters). Seabiscuit is a type of BISCUIT that was traditionally eaten by sailors on long voyages, while shipbiscuit is a type of BISCUIT that was used as a form of currency in the 18th century.