pilot bread vs hardtack

pilot bread and hardtack both are nouns.

Word	Noun	Adjective	Verb	Adverb
pilot bread	Yes	No	No	No
hardtack	Yes	No	No	No

As nouns, pilot bread and hardtack are synonyms defined as:

pilot bread and hardtack: very hard unsalted biscuit or bread; a former ship's staple

Other synonyms of pilot bread include pilot biscuit, sea biscuit, ship biscuit.

pilot bread (noun)	hardtack (noun)
very hard unsalted biscuit or bread; a former ship's staple	very hard unsalted biscuit or bread; a former ship's staple
	a mountain mahogany