1. [adj]  unwilling or unable to forgive or show mercy; "a surly unforgiving old woman"
2. [adj]  harsh and severe; "I hope I'm not being uncharitable but he really is a bore"; "unjust and uncharitable criticism"
3. [adj]  not to be placated or appeased or moved by entreaty; "grim determination"; "grim necessity"; "Russia's final hour, it seemed, approached with inexorable certainty"; "relentless persecution"; "the stern demands of parenthood"

UNFORGIVING is a 11 letter word that starts with U.