• heartack,
• hardwick,
• hardrock,
• cardtock,
• hardtck,
• hakmatack,
• hardrack,
• harrdtack,
• hartack,
• hardtak,
• hradtack,
• hardtackk,
• harttack,
• hardpack,
• hardtakk,
• harrdhack,
• hardhck,
• hardhakc,
• hardhackk,
• Hordoak

• hard disk,
• hard tick,
• Hardwick,
• hardage,
• haystack,
• hard disc.

The adjective form of the word "hardtack" is "hardtacky".

The plural of the "hardtack" can be the "hardtacks".

The singular of the "hardtack" can be the "hardtack".