14 C.F.R. § 437.3
Envelope expansion means any portion of a flight where planned operations will subject a reusable suborbital rocket to the effects of altitude, velocity, acceleration, or burn duration that exceed a level or duration successfully verified during an earlier flight.
Exclusion area means an area, within an operating area, that a reusable suborbital rocket's instantaneous impact point may not traverse.
Operating area means a three-dimensional region where permitted flights may take place.
Permitted vehicle means a reusable suborbital rocket operated by a launch or reentry operator under an experimental permit.
Reentry impact point means the location of a reusable suborbital rocket's instantaneous impact point during its unpowered exoatmospheric suborbital flight.
14 C.F.R. §437.3