n. [ Cf. F. irrésistibilité. ] The quality or state of being irresistible, irresistibleness. [ 1913 Webster ]
a. [ Pref. ir- not + resistible: cf. F. irrésistible. ] That can not be successfully resisted or opposed; superior to opposition; resistless; overpowering;
An irresistible law of our nature impels us to seek happiness. J. M. Mason. [ 1913 Webster ]
n. Quality of being irresistible. [ 1913 Webster ]
adv. In an irresistible manner. [ 1913 Webster ]