The captain or member of the crew of a privateer(noun)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "privateersman" in a sentence
"The privateersman was a gentleman adventurer, a protected pirate, a social highwayman of the waters."
"A pirate, indeed, in those days, was synonymous with the individual who was termed a privateersman at the time of the Napoleonic wars."
"I do not, therefore, consider that privateering is worse than any other species of warfare, or that the privateersman is a whit more reckless or brutal than soldiers or men-of-war's men in the hour of victory in the king's service. ""