A giant sword is often referred to as an "oversized sword" or a "greatsword." These terms are used to describe swords that are larger than average, often depicted in works of fiction, video games, or fantasy art. The specific name used for a giant sword can vary depending on the context and the fictional universe in which it is depicted.

In certain fantasy settings or video games, giant swords may have unique names or classifications specific to that particular fictional world. These names are often invented by the creators and may reflect the lore, mythology, or aesthetic of the fantasy setting. Examples of fictional names for giant swords include the "Buster Sword" from Final Fantasy VII or the "Dragonslayer" from Berserk.

However, it's important to note that in the realm of real-world historical weaponry, oversized swords are not commonly recognized as distinct types with specific names. Traditional historical swords, such as the longsword or greatsword, can vary in size, but the term "giant sword" is more commonly used to describe exaggerated or fictional depictions rather than a specific type of weapon with a unique name.