Brigantine Pirate Sword, Wood Grip
The Brigantine was a powerful type of ship that was highly sought after by pirates. It was a roughly 150 ton ship, capable of carrying from 10-12 guns and a crew of up to 100 men. These ships were for big-boy pirates who didn't have to hide or run from their enemies. Sometimes called "skirmish ships," the Brigantines were made for combat, and it was a brave or powerful pirate who commanded one. Brigantines were also occasionally used by the Royal Navy to hunt down pirates, but for the most part, pirate hunting ships usually were a little larger still. Regardless, the larger Brigantines could gobble up the more common sloops like hor doeuvres (mental note: never use the word hor doeuvres in writing again. Pain in the butt getting the spelling and just doesn't look right). Although the sloops were a bit faster and occasionally carried more guns, the Brigantines could take much more punishment and could hold more men.
The average pirate ship, a sloop, was a one-masted ship that could carry about 50-75 men and as many as (but rarely) 14 guns. Some sloops were larger than that, but in almost all versions, a Brigantine was a more favorable ship. In the pecking order of ships, Brigantine's were above Sloops and Barqs, but below the mighty Frigates. Few pirates captained Brigantines. Even fewer ever captained Frigates. Blackbeard had one (the Queen Anne's Revenge), but few others had the means to take and keep a warship.
The Brigantines carried two sails, but used a combination of square sails and "fore-and-aft" sales to give it versatility on the sea (which means that it could both outrun you AND outgun you). Of course, shipping vernacular changed and morphed throughout history, and the exact specifics of the Brigantine mutated with it, but all seem to agree that brigantines had two masts and were larger ships than Sloops.
See Strongblade's Brigantine Pirate Sword, Wood Grip