musketoon

noun2

1. •
   (historical) A firearm, similar to a musket but with a shorter barrel and a large bore.

   • And d'Artagnan set the example. Then, turning toward Planchet, he made him a sign to uncock his musketoon. The Englishmen, convinced of these peaceful proceedings, sheathed their swords grumblingly. — 1844
2. •
   (no longer used) One who is armed with such a musket.