Wiktionary
n. A poleaxe with a modified hammerhead and a spike mounted on the top of the pole.
Wikipedia
A bec de corbin is a type of pole weapon that was popular in medieval Europe. The name is Old French for "raven's beak" or "beak of the crow". Similar to the Lucerne hammer, it consists of a modified hammer's head and spike mounted atop a long pole. Unlike the Lucerne hammer, the bec de corbin was used primarily with the 'beak' or fluke to attack instead of the hammer head. The hammer face balancing the beak was often blunt instead of the multi-pronged Lucerne, and the beak tended to be stouter; better designed for tearing armor. Also, the spike mounted on the top of head was not nearly as long and thin as in the Lucerne. Bec de corbin occasionally becomes a catchall for any type of warhammer, such as a maul or a horseman's pick.
A similar name, bec de faucon (meaning "falcon's beak"), refers to a related weapon called a poleaxe or, more specifically, to the hook on its reverse side.