To be "infirm of purpose" is to be at the mercy of the artful or at the disposal of accident.
The contemplation of the infirm and lonely steed overcame him.
But the infirm are always cunning—he breathed not a suspicion.
Can they give beauty to the deformed, strength to the weak, or health to the infirm?
The Duke of Lerma, infirm and enfeebled by years, was unable to confront ...