Not capable of being restored to a good spiritual or moral state, or reformed from a life of vice or undesirable behaviour; irredeemable; (also in weaker, more general use) not able to change; incorrigible. Now somewhat archaic.

Of land: that cannot brought under cultivation or made fit for habitation; uncultivable.

That cannot be regained, retrieved, or recovered.

With the. Unreclaimable people as a class. Also: that which is unreclaimable. Compare sense A. 1. rare after 17th century.