infirm in WordNet English dictionary

1. lacking bodily or muscular strength or vitality
   "a feeble old woman"; "her body looked sapless"
   decrepit  debile  feeble  infirm  rickety  sapless  weak  weakly 
   
2. lacking firmness of will or character or purpose
   "infirm of purpose; give me the daggers" - Shakespeare
   infirm