A giant katana is commonly referred to as an "ōdachi" or "nodachi." These terms are often used interchangeably, though there can be slight variations in their definitions depending on historical context.

The ōdachi and nodachi are both terms used to describe exceptionally long Japanese swords. While there isn't a strict length requirement to define a sword as an ōdachi or nodachi, they typically have a blade length of around 90 centimeters (35 inches) or longer. Some examples of ōdachi/nodachi blades could reach lengths of over 100 centimeters (39 inches) or even more.

These giant swords were primarily used in specific historical contexts, such as during battles or ceremonies. They were often wielded by skilled samurai warriors who had the strength and training to handle their size and weight. Due to their longer reach and cutting power, ōdachi and nodachi swords were effective against multiple opponents and in open-field combat.

The distinction between ōdachi and nodachi can be somewhat debated among historians and enthusiasts. In some interpretations, nodachi is used to describe a sword with an extended handle to accommodate the use of both hands, while ōdachi is a general term for any large sword regardless of the handle design. However, the terms are sometimes used interchangeably, and the specific usage can vary depending on the region or historical period.

It's important to note that giant katanas, such as ōdachi and nodachi, are primarily historical artifacts or collectibles today. Their size and weight make them impractical for combat, and they are more commonly appreciated for their craftsmanship, historical significance, and as display pieces.