Piracy was a human term describing a robbery committed at sea, or sometimes on the shore, without a commission from a sovereign nation (robbery with sovereign commission was called privateering, and was distinct from piracy). In the Post Diaspora era, humanity saw a resurrection of this ancient criminal tradition in the form of space piracy.
The Silesian Confederacy was haunted by pirates. Both the Star Kingdom of Manticore and the Andermani Empire battled local pirate ships in the Confederacy to assure the safety of their trading lines.
As far as the Royal Manticoran Navy was concerned, piracy was punishable by death. Under the terms of the Cherwell Convention, star nations could treat slavers as pirates. (HH6)
The Ranier War saw the destruction of the Ranier Pirates in the Ranier System. (Companion, SITS)
The Kersey Association was a pirate navy whose actions against the Manitoban Republic resulted in an amendment to the Deneb Accords. (HH6, HH7)
After the fall of the Office of State Security and the annexation of the Silesian Confederacy, many crews of the Silesian Confederate Navy and the State Security Naval Forces (Liberation Force in Exile, People's Navy in Exile, People's First Liberation Squadron) became pirates, warlords, or sold their warships.