hardtack

noun

Etymology: From hard + tack.

1. A large, hard biscuit made from unleavened flour and water; formerly used as a long-term staple food aboard ships.

   “Meronym: reefer's nut”

   “Philander went into the next room[…]and came back with a salt mackerel that dripped brine like a rainstorm. Then he put the coffee pot on the stove and rummaged out a loaf of dry bread and some hardtack.”