privateer (n.)

1660s, "private man of war, armed vessel owned and officered by private persons, usually acting under commission from the state," from private (adj.), probably on model of volunteer (n.), buccaneer. From 1670s as "one commanding or serving on a privateer." As a verb, 1660s (implied in privateering) "to cruise on a privateer, to seize or annoy an enemy's ships and commerce."