a person or thing that raids.

a commando, ranger, or the like, specially trained to participate in military raids.

a light, fast warship, aircraft, etc., used in such a raid.

a person who seizes control of a company, as by secretly buying stock and gathering proxies.

Informal . a person who works within an organization for the purpose of gathering evidence of wrongdoing.

noun

bandit , buccaneer , freebooter , highwayman , hijacker , looter , marauder , pilferer , pillager , pirate , plunderer , privateer , rustler , thief