pirate, buccaneer, sea robber, sea rover -- (someone who robs at sea or plunders the land from the sea without having a commission from any sovereign nation)
pirate, pirate ship -- (a ship that is manned by pirates)
Overview of verb pirate
The verb pirate has 2 senses
pirate -- (copy illegally; of published material)
commandeer, hijack, highjack, pirate -- (take arbitrarily or by force; "The Cubans commandeered the plane and flew it to Miami")