A halberd is a two-handed polearm: an axe blade topped with a spike, mounted on a long wooden shaft, often with a hook or thorn on the back of the blade for pulling riders off horses. It was in prominent use in Europe from the 13th to the 16th centuries.
Halberds were typically about 2 to 2.5 metres (6.6 to 8.2 feet) long, letting infantry strike, thrust, and hook at a distance. Today they survive mainly as ceremonial weapons, carried for example by the Swiss Guard at the Vatican.
Source: Wikipedia: Halberd