A katana without a tsuba is often referred to as a "tsuba-less katana" or simply a "koshirae katana." The term "koshirae" refers to the entire ensemble or set of fittings on a Japanese sword, including the handle, scabbard, and any additional ornaments or accessories.

The tsuba is the handguard on a katana, positioned between the blade and the handle. Its purpose is to protect the hand and provide stability during sword techniques. However, there are instances where a katana is intentionally made or displayed without a tsuba for various reasons.

A tsuba-less katana may be used for specific martial arts training or practices where the absence of a tsuba allows for a more comfortable grip, lighter weight, or greater maneuverability. It can provide a different experience in handling and wielding the sword.

In some cases, a tsuba-less katana may be used for ceremonial or display purposes. It can showcase the blade's craftsmanship or highlight specific artistic elements, such as hamon (the temper line) or hada (the grain pattern of the steel).

It's worth noting that a katana without a tsuba should still have other essential components such as the habaki (a metal collar that secures the blade in the scabbard), seppa (spacer washers), and the tsuka (handle) properly wrapped with tsuka-ito (handle wrapping).

Overall, a katana without a tsuba can have different applications depending on the purpose, whether it be for specific training, artistic display, or other specialized uses.