UNMERCIFUL Meaning of UNMERCIFUL in English a. 1.Merciless, cruel, inexorable, inhuman, pitiless, unpitying, ruthless, unrelenting, unsparing.2.( Colloq. ) Exorbitant, extravagant, unconscionable, excessive. Soule. Dictionary of English synonyms. Словарь английских синонимов. 2012