A double-headed spear is commonly referred to as a "double-headed spear" or a "bidental." The term "bidental" originates from the Latin word "bidentalis," which means "two-toothed."

A double-headed spear features a spearhead on each end of the shaft, allowing for strikes or thrusts from either side. The design of the spearhead can vary, but it typically has a symmetrical shape with a point on each end.

Double-headed spears have been used by various cultures and civilizations throughout history. They offered advantages in combat situations by allowing for multiple attacks without the need to reposition or reverse the spear. They were particularly effective in formation-based warfare, where soldiers could attack from both sides simultaneously.

It's worth noting that there are other terms used to describe similar weapons. For example, the term "double-headed pike" or "double-headed halberd" is sometimes used to describe similar polearms with axe-like or hook-like elements in addition to the spearheads.

Ultimately, the specific term used may vary depending on cultural or historical contexts, but "double-headed spear" or "bidental" are commonly understood terms for this type of weapon.