Infirm meaning
An old and sickly person is an example of someone who is infirm.
When you cannot make or stick to a decision and are weak-willed, this is an example of being infirm.
An infirm foundation.
An infirm title to property.
The thought is that you see an episode of observation, experiment, or reasoning as confirming or infirming a hypothesis depending on whether your probability for it increases or decreases during the episode.