Corporate is SCA shorthand used to refer to things which are occurring or mandated by the modern SCA Corporation. It is sometimes referred to as Imperial, although that is an archaic usage that is no longer common. It is an alternate way of saying (or meaning) "SCA-wide."
Common usage is in terms like "This new rule just came down from Corporate." or "Corporate says we can't do that." or "Such and such happened at the Corporate level."
The old usage dates from when the BoD styles themselves Imperial Electors, in an attempt to try to stay involved in the game. But eventually it became clear that the business of running a modern Not-for-Profit needed to be decoupled from the reenactment activities.