Entry 1 sense Webster, 1913 Unmerciful /ən-mẽrs'-ĭf-əl/ · Un·mer·ci·ful · IPA /ʌnˈmɝsɪfl̩/ 01 a. Not merciful; indisposed to mercy or grace; cruel; inhuman; merciless; unkind. 1. Not merciful; indisposed to mercy or grace; cruel; inhuman; merciless; unkind.