Privateer
PRIVATEE'R, noun [from private.] A ship or vessel of war owned and equipped by a private man or by individuals, at their own expense, to seize or plunder the ships of an enemy in war. Such a ship must be licensed or commissioned by government, or it is a pirate.
PRIVATEE'R, verb intransitive To cruise in a commissioned private ship against an enemy, for seizing their ships or annoying their commerce.