Under-Lease
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
In conveyancing. A lease granted by one who is himself a lessee for years, for any fewer or less number of years than he himself holds. If a deed passes all the estate or time of the termor, it is an assignment; but, if it be for less portion of time than the whole term, it is an under-lease, and leaves a reversion in the termor.
4 Kent, Comm. 96.