A raider can refer to different things depending on the context. Here are the different definitions of a raider:

• Corporate Raider: A person who attempts a usually hostile takeover of a business corporation by purchasing a controlling interest of stock, as in corporate raider.

• Warship or Aircraft: A light, fast warship, aircraft, etc., used in a raid.

• Informal: A person who works within an organization for the purpose of gathering information or intelligence.

In summary, a raider can refer to a person who attempts a hostile takeover of a business corporation, a type of warship or aircraft used in a raid, or a person who works within an organization for the purpose of gathering information or intelligence.