(2)"estate" includes-(a)any land subject to the payment of land-revenue, either immediately or prospectively, for the discharge of which a separate engagement has been entered into with [the Government] ;(b)any land which is entered on the revenue-roll as separately assessed with land-revenue (whether the amount of such assessment be payable immediately or prospectively), although no engagement has been entered into with [the Government] for the amount of revenue so separately assessed upon it as a whole;(c)any land being the property of [the Government] of which the Board shall have directed the separate entry on the general register hereinafter mentioned [or on any other register prescribed for the purpose by rule made under this Act] ;
