infirm

adj

1. Weak or ill, not in good health.

   “He was infirm of body but still keen of mind, and though it looked like he couldn't walk across the room, he crushed me in debate.”

   “[…] Here I stand your slave, A poor, infirm, weak, and despis’d old man.”

   “There will be special drop-off points at all polling stations for vehicles conveying voters who are sick, infirm, or disabled.”

2. Irresolute; weak of mind or will.

   “Infirm of purpose! Give me the daggers: […]”

   “[…] vehement passion does not always indicate an infirm judgment.”

3. Frail; unstable; insecure.

   “He who fixes upon false Principles, treads upon Infirm ground, and so sinks […]”

verb

1. To contradict, to provide proof that something is not.

   “The thought is that you see an episode of observation, experiment, or reasoning as confirming or infirming a hypothesis depending on whether the probability of it being correct increases or decreases during the episode.”