'Hardtack' definitions:

Definition of 'hardtack'

From: WordNet
noun
Very hard unsalted biscuit or bread; a former ship's staple [syn: hardtack, pilot biscuit, pilot bread, sea biscuit, ship biscuit]
noun
A mountain mahogany

Definition of 'Hardtack'

From: GCIDE
  • Hardtack \Hard"tack`\ or Hard-tack \Hard"-tack`\(h[aum]rd"t[a^]k`), n.
  • 1. A name given by soldiers and sailors to a kind of unleavened hard biscuit or sea bread. Called also {pilot biscuit}, pilot bread, ship biscuit and ship bread [1913 Webster]
  • 2. Any of several mahogany trees, esp. the {Cercocarpus betuloides}. --MW10 [PJC]