Definition of "irresistable"

The suddenness of this shock must prove irresistable; the Count and those about him will be borne down; the rest will take to flight; the friends of Bernabò will rise and liberate his sons, while I seize one of the gates and secure a retreat […]

1830, David Syme, The Fortunes of Francesco Novello Da Carrara, Lord of Padua

The victim is an irresistable, insane subject of the peculiar trance, oblivious to his acts, and ofttimes unconscious of them afterward. During the attack he is in no way the same actor.

1895, Medical Review, volumes 30-31, page 423