"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."
2.AdjectiveIrresolute; weak of mind or will.
3.AdjectiveFrail; unstable; insecure.
4.VerbTo 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."