Not improved; not made better or wiser; not advanced in knowledge, manners, or excellence. [1913 Webster]
Not used; not employed; especially, not used or employed for a valuable purpose; as, unimproved opportunities; unimproved blessings. Cowper. [1913 Webster]
Not tilled, cultivated, or built upon; yielding no revenue; as, unimproved land or soil. [1913 Webster]